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PH in new tank



 
 
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  #1  
Old April 17th 05, 06:48 PM
smartbomb
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Default PH in new tank

On thrid week of patiently waiting while my live rock, live sand, salt
water and bacteria cycle.

Ph is still 7.4-7.8 I was under the assumption that I should be using
distilled water to top off evaporated tank. Then someone told me
distilled had a ph of 5.

Any suggestions?

  #2  
Old April 18th 05, 04:07 AM
Pszemol
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Posts: n/a
Default

"smartbomb" wrote in message oups.com...
Ph is still 7.4-7.8 I was under the assumption that I should be using
distilled water to top off evaporated tank. Then someone told me
distilled had a ph of 5.


pH of distilled water is not important in this case.

Low pH of distilled water is caused by small amount of CO2
dissolved in it. This effect is normal, due to the surface air access.
The same amount of CO2 will dissolve in your tank water,
but it will not cause pH drop due to buffers existing in the water.
Distilled water is lacking buffers so CO2 influences pH strongly.

Don't know what salt mix you use and how do you measure pH
but maybe you need more reef buffers in your water...
Check your alkalinity levels.

Also read this very informative article:
http://www.advancedaquarist.com/issu...e2002/chem.htm
Be carefull in playing with pH level - even relatively low pH level
like yours is better than large pH variations you might cause...

The bottom line is: adding distilled water will NOT drop your
pH level in the tank. Adding distilled (or purified in other ways,
i.e. RO/DI) water is the only way of properly replace evaporated
water and adjust salnity level to the normal level.

Feel free to ask if you need to know more.
  #3  
Old April 18th 05, 06:43 AM
George
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Posts: n/a
Default


"Pszemol" wrote in message
...
"smartbomb" wrote in message
oups.com...
Ph is still 7.4-7.8 I was under the assumption that I should be using
distilled water to top off evaporated tank. Then someone told me
distilled had a ph of 5.


pH of distilled water is not important in this case.

Low pH of distilled water is caused by small amount of CO2
dissolved in it. This effect is normal, due to the surface air access.
The same amount of CO2 will dissolve in your tank water,
but it will not cause pH drop due to buffers existing in the water.
Distilled water is lacking buffers so CO2 influences pH strongly.

Don't know what salt mix you use and how do you measure pH
but maybe you need more reef buffers in your water...
Check your alkalinity levels.

Also read this very informative article:
http://www.advancedaquarist.com/issu...e2002/chem.htm
Be carefull in playing with pH level - even relatively low pH level
like yours is better than large pH variations you might cause...

The bottom line is: adding distilled water will NOT drop your
pH level in the tank. Adding distilled (or purified in other ways,
i.e. RO/DI) water is the only way of properly replace evaporated
water and adjust salnity level to the normal level.

Feel free to ask if you need to know more.



Hmmm. See my earlier post called "RO and pH issues.


  #4  
Old April 18th 05, 02:58 PM
Pszemol
external usenet poster
 
Posts: n/a
Default

"George" wrote in message news:[email protected]_s21...
Hmmm. See my earlier post called "RO and pH issues.


You do NOT need to add buffers to the top off RO water.
You do NOT need to add Calcium additives either.

Try not to reinvent the wheel - read more chemistry
articles and do this stuff the right way.

If 100% of marine tank keepers do not play with top-off
water, also, if the Nature just drops rain water without any
added buffering to the ocean - you do not need to process ro
water either... Acid pH level of RO water is not important!
If you leave it in the bucket for several hours any excess of
CO2 will escape the water (and other gases will equalize as well).
After several hours in the bucket the water will have NORMAL
level of CO2 and other gases (Nitrogen, Oxygen) dissolved in it.
So in terms of gases, what RO membrane stops or leaves behind there
is not important! http://en.wikipedia.org/wiki/Partial_pressure

If your tank water is unable to support high calcium
levels and the level is 280mg/l check the water parameters
to find out the reason why it is this way. There are several
good articles about keeping right calcium levels, check out
the website I gave the link to before...
Adding calcium to the ro water and then pouring this
water to the tank water might cause calcium precipitation
and covering everything with white snow... If your tank
water does not support high calcium levels you will not
force the water to high levels this way... sorry.
Do not experiment unless you are sure what you are doing
(i.e. have good background of basic chemistry courses).

Change your focus from your RO - your top off water or its pH is NOT
the problem here. Try to focus on your tank water parameters instead.
  #5  
Old April 19th 05, 12:43 AM
George
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Posts: n/a
Default


"Pszemol" wrote in message
...
"George" wrote in message
news:[email protected]_s21...
Hmmm. See my earlier post called "RO and pH issues.


You do NOT need to add buffers to the top off RO water.
You do NOT need to add Calcium additives either.

Try not to reinvent the wheel - read more chemistry
articles and do this stuff the right way.


I have two years of college chemistry, have a masters in Geology, and have
raised fish for most of my 46 years. What more chemistry do you think I need in
order to understand that if you add unbuffered water with a pH of 5.0, you are
going to dilute the buffers in the existing salt water, and will affect the pH,
especially since that make up water has a lot of CO2 in it with a pH of 5.0?

If 100% of marine tank keepers do not play with top-off
water, also, if the Nature just drops rain water without any
added buffering to the ocean


The oceans are miles deep, so overall rainwater has little affect. However, the
topmost layer at the surface is in fact affected by rainwater.

- you do not need to process ro
water either... Acid pH level of RO water is not important!


If that is the case, you won't mind if I pour a bottle of HCL into your
aquarium, since pH is not important to you.

If you leave it in the bucket for several hours any excess of
CO2 will escape the water (and other gases will equalize as well).


This is incorrect. The RO water I tested for pH was in an unsealed five gallon
plastic container, and had been made at least four days before I tested it. The
pH was 5.0, indicating high concentrations of CO2 in the water. Once I add
buffers and aerated the water, the pH rose to 7.5.

After several hours in the bucket the water will have NORMAL
level of CO2 and other gases (Nitrogen, Oxygen) dissolved in it.


Wrong, wrong, wrong. Make up a gallon of RO water, test the pH, then leave the
water in an unsealed plastic container for four days, and then test the pH
again. Then come back and tell me that the pH has stabilized to an acceptable
reading (5.0, in my case, is not acceptable, and since the pH was at 5.0 after
four days, I can imagine what the pH level was at one day. I plan to find out
tonight).

So in terms of gases, what RO membrane stops or leaves behind there
is not important! http://en.wikipedia.org/wiki/Partial_pressure


See above.

If your tank water is unable to support high calcium
levels and the level is 280mg/l check the water parameters
to find out the reason why it is this way.


I'm sure it is able to support higher calcium levels. The thing is that all
marine reef tanks use up calcium so it has to be added. I hadn't added any
calcium since my last partial water change (about a month). That is why the
calcium levels were low. I had been adding buffer periodically, however, which
is why I was suprised that my pH was only 7.5. I have a wave maker which causes
a lot of evaporation, so I have to add makeup water frequently. This is why I
am convinced that the unbuffered RO water was the culprit.

There are several
good articles about keeping right calcium levels, check out
the website I gave the link to before...
Adding calcium to the ro water and then pouring this
water to the tank water might cause calcium precipitation
and covering everything with white snow...


I only add enough clacium to the RO water to make it the same as my tap water,
which is 60 mg/L, not enough to cause precipitation since even at that level,
adding it to the tank water (which has a concentration of 280 mg/L) is still
diluting the tank water. After a couple of days, I will check the calcium
concentration in the tank water to see if addition calcium is needed.

If your tank
water does not support high calcium levels you will not
force the water to high levels this way... sorry.


Why would my tank water not support high calcium levels? The only reason for
the levels to drop in the first place is because the animals and macroalgae in
the tanks are using it. That is why you have to add calcium periodically to
reef tanks. I have 4 inches of aragonite sea sand in the tank and three inches
of it in the refugium, so the pH isn't going to fall below about 7.5.

Do not experiment unless you are sure what you are doing
(i.e. have good background of basic chemistry courses).


See above. Ok Einstein, what is the vapor pressure of CO2? Note. I've had
reef tanks for 14 years (but have only used RO for the last two years), have a
maroon clown fish that is also 14 years old, have a 1,200 gallon garden pond,
and have raised tropical fish since I was 11 years old. I am also a geologist
(more specifically, a hydrogeologist).

Change your focus from your RO - your top off water or its pH is NOT
the problem here. Try to focus on your tank water parameters instead.


The other parameters are fine Temp = 78 F, Nitrate = 0, Nitrite = O, Ammonia =
0, hydrometer reading 1.023.

The problem is NOT the tank water. The problem IS the make up water. I never
had this problem when using an ion resin filter (DI). It was only after I
started using the RO filter that the problem occurred. Note: I took the RO
water that had a pH reading of 5.0 and added buffers and calcium to it, to bring
it up to a pH of 8.0 and a calcium concentration of 60 mg/L. I did this last
night. Today, I added this water (three gallons) slowly to the tank. The tank
water is now at 8.0 and the calcium reading is at 360, which is just below the
normal level for a tank after you've added fresh seawater to it. The pH is
still low, so I will change it over the course of the next few days.


  #6  
Old April 19th 05, 05:00 AM
Pszemol
external usenet poster
 
Posts: n/a
Default

"George" wrote in message news:[email protected]_s72...
I have two years of college chemistry, have a masters in Geology, and have
raised fish for most of my 46 years. What more chemistry do you think I need in
order to understand that if you add unbuffered water with a pH of 5.0, you are
going to dilute the buffers in the existing salt water, and will affect the pH,
especially since that make up water has a lot of CO2 in it with a pH of 5.0?


I think it is going too far... Look, I do not want to make an enemy out of you,
but I still think you have it wrong. I am trying to explain what I know, but
you do not make it easy... I would fail as a teacher - I am happy I am not one
of them... ;-)

Mr. Boomer! Where are you!??! You had a gift of explaining chemistry to everybody...

Let me point some simple facts again, you figure out what you are missing:
- it does NOT take a lot of CO2 to lower pH of purified water with no buffers,
in fact, it takes VERY LITTLE CO2 to change pH, due to the lack of buffers.
- it does not *dilute* buffers, it rather brings them BACK to the level
before water evaporated leaving higher concentration of buffers there.
When water evaporates it does not take with it your buffers, the same
is true when opposite process happens: you do not "need" to add buffers
to replace evaporated water (but of course you are free to do so...)
- animals building their tissues (and their metabolic products) use up
the buffers, not processes of evaporation/toping off with purified water.
So the problem is NOT in your top-off purified water - that is for sure...
If you had alk level 10, then you let 10 gallons of water to evaporate and
then you add 10 gallons of purified water you will be back to ~10 alk level.
- pH is not an "easy" unit of measurement, so simple math does NOT apply to mixing
(mixing equal amounts of water of pH 5 with water pH 8 DOES NOT GIVE you pH 7!)
You should not worry adding small amounts of purified water with pH 5.
It will simply NOT AFFECT significantly the pH of your tank water.

- you do not need to process ro
water either... Acid pH level of RO water is not important!


If that is the case, you won't mind if I pour a bottle of HCL into your
aquarium, since pH is not important to you.


Wrong. Adding purified water at pH 5 IS NOT THE SAME as adding
a bottle of HCl to your fish tank... And you should know it better.
I would not mind to pour purified water (without CO2) with a *small*
addition of HCl to cause *same pH 5 of the water*. That is correct:
I wouldn't mind!
The single serious mistake in your thinking process is that you seem to
miss the fact that it takes VERY LITTLE of acid to drop pH of pure water
(pure = without any buffers in it...) Based on this mistake the rest of
conclusions is wrong, too.

This is incorrect. The RO water I tested for pH was in an unsealed five gallon
plastic container, and had been made at least four days before I tested it. The
pH was 5.0, indicating high concentrations of CO2 in the water. Once I add
buffers and aerated the water, the pH rose to 7.5.


It did not indicate "high concentrations of CO2"! (high/low is very vague anyway...)
See, this is exactly what takes you off track here...
High buffering capacity of water means it is hard to CHANGE pH of water
with addition of acid. Low buffering capacity of water means it is very
easy to change pH of water with even very small addition of acid (like CO2).

If you do not believe me, try to challenge yourself with calculation of
HOW MUCH CO2 does it take to change pH of purified water (18Mohms) from 7 to 5.
I asure you, it does not take much CO2 to make significant drop in pH
assuming there is no buffers in the water. In fact, by adding buffers to the
water you probably DID NOT CHANGE THE AMOUNT OF DILUTED CO2 in the bucket...
So pouring the bucket with or without buffers you actually add THE SAME amount
of CO2 into your tank. The buffer just makes you feel better, you see pH 8 :-)

After several hours in the bucket the water will have NORMAL
level of CO2 and other gases (Nitrogen, Oxygen) dissolved in it.


Wrong, wrong, wrong. Make up a gallon of RO water, test the pH, then leave the
water in an unsealed plastic container for four days, and then test the pH
again. Then come back and tell me that the pH has stabilized to an acceptable
reading (5.0, in my case, is not acceptable, and since the pH was at 5.0 after
four days, I can imagine what the pH level was at one day. I plan to find out
tonight).


After couple of hours of aerating, the level of CO2 in solution will reach
equilibrium with the ambient CO2 levels. The same will happen with oxygen and
nitrogen. This *very small* amount of CO2 will always cause significant pH drop
in water lacking buffers, but this effect should not worry us, tank keepers!
There is simply nothing in the water to neutralize acidity of dissolved CO2
- oxygen or nitrogen solutions are neutral and they do not cause any pH shift.

I'm sure it is able to support higher calcium levels. The thing is that all
marine reef tanks use up calcium so it has to be added. I hadn't added any
calcium since my last partial water change (about a month). That is why the
calcium levels were low. I had been adding buffer periodically, however, which
is why I was suprised that my pH was only 7.5. I have a wave maker which causes
a lot of evaporation, so I have to add makeup water frequently. This is why I
am convinced that the unbuffered RO water was the culprit.


And this was my point - you just need to increase dosage of buffers&calcium
into your tank due to the animals activity and NOT due to the effects you
have discribed ("diluting your buffers with RO water containing a lot of CO2").
You want to add buffers to ro-water before adding it to the tank? Fine...
But this is not important. The same effect you would achieve adding buffers
directly to the tank. The dosage of buffers and calcium should be related
to the uptake of animals/plants/algae you keep in your tank and NOT related to
the pH or amount of water you use to top-off the tank to replace what has evaporated.

I only add enough clacium to the RO water to make it the same as my tap water,
which is 60 mg/L, not enough to cause precipitation since even at that level,
adding it to the tank water (which has a concentration of 280 mg/L) is still
diluting the tank water. After a couple of days, I will check the calcium
concentration in the tank water to see if addition calcium is needed.


As I said before, switch your focus from the bogus effects of "diluting"
your buffers to REAL effects of animals uptake of buffers/calcium...
Adding RO water just REPLACES WHAT HAS EVAPORATED. It does not affect
significantly anything else in your tank in comparison to animals uptake.

Why would my tank water not support high calcium levels? The only reason for
the levels to drop in the first place is because the animals and macroalgae in
the tanks are using it. That is why you have to add calcium periodically to
reef tanks. I have 4 inches of aragonite sea sand in the tank and three inches
of it in the refugium, so the pH isn't going to fall below about 7.5.


So why do you worry about minuscule levels of CO2 in your RO water?

Do not experiment unless you are sure what you are doing
(i.e. have good background of basic chemistry courses).


See above. Ok Einstein, what is the vapor pressure of CO2? Note. I've had
reef tanks for 14 years (but have only used RO for the last two years), have a
maroon clown fish that is also 14 years old, have a 1,200 gallon garden pond,
and have raised tropical fish since I was 11 years old. I am also a geologist
(more specifically, a hydrogeologist).


Well- true, I am not Einstein - in fact, I do not even have a degree in chemistry.
So I should probably shut up and wait for you to easily figure out how much
CO2 does it take to lover pH of purified water from 7 to 5... Then you can
compare how much CO2 does it take to drive normal sea water to pH 5...
Please do yourself a favor and present these calculations.

The problem is NOT the tank water. The problem IS the make up water.


Ok... your are wrong. But I am not going to continue this thread.
I understand you invested too much in this discussion and it will be hard for you
now to admit you made a mistake... Especially after you were throwing your degree
at us here and years of fish keeping experience...
So I will shut up now and leave you alone. Your tank - your problem... :-)

Maybe in the last act of desperation I will suggest following reading:
http://www.advancedaquarist.com/issues/may2002/chem.htm
There are some charts in this article - try to match amount of CO2
which will cause pH drop to 5 in water having 0 buffering capacity.
  #7  
Old April 19th 05, 06:24 AM
George
external usenet poster
 
Posts: n/a
Default


"Pszemol" wrote in message
...
"George" wrote in message
news:[email protected]_s72...
I have two years of college chemistry, have a masters in Geology, and have
raised fish for most of my 46 years. What more chemistry do you think I need
in order to understand that if you add unbuffered water with a pH of 5.0, you
are going to dilute the buffers in the existing salt water, and will affect
the pH, especially since that make up water has a lot of CO2 in it with a pH
of 5.0?


I think it is going too far... Look, I do not want to make an enemy out of
you,
but I still think you have it wrong. I am trying to explain what I know, but
you do not make it easy... I would fail as a teacher - I am happy I am not one
of them... ;-)


If you don't want to make an enemy of me then don't make suggestions that I
learn something about basic water chemistry.

Mr. Boomer! Where are you!??! You had a gift of explaining chemistry to
everybody...

Let me point some simple facts again, you figure out what you are missing:
- it does NOT take a lot of CO2 to lower pH of purified water with no buffers,
in fact, it takes VERY LITTLE CO2 to change pH, due to the lack of buffers.
- it does not *dilute* buffers, it rather brings them BACK to the level
before water evaporated leaving higher concentration of buffers there.


Please explain how water with no buffers can bring water with buffers "BACK to
the level before water evaporated leaving higher concentration of buffers
there". My sal****er was already depleted of buffer before I added the RO water
(as indicated by the low pH - 7.5 as opposed to 8.4). If the purified water
with no buffer has a low pH due to its CO2 content, adding this low pH water to
the salt water will in fact deplete the buffer in that sal****er because it will
use up however much buffer it takes to neutralize the CO2.

When water evaporates it does not take with it your buffers,


No it does not. What takes the buffers is CO2, which is added to the water by
micro/macroalgae at night, and by the animals in the aquarium.

the same
is true when opposite process happens: you do not "need" to add buffers
to replace evaporated water (but of course you are free to do so...)
- animals building their tissues (and their metabolic products) use up
the buffers, not processes of evaporation/toping off with purified water.


So do plants. I never said it was a problem of evaporation.

So the problem is NOT in your top-off purified water - that is for sure...
If you had alk level 10, then you let 10 gallons of water to evaporate and
then you add 10 gallons of purified water you will be back to ~10 alk level.


Unless something else, such as the plants and animals in the tank are using up
the buffer, which we've established that they do.

- pH is not an "easy" unit of measurement, so simple math does NOT apply to
mixing
(mixing equal amounts of water of pH 5 with water pH 8 DOES NOT GIVE you pH
7!)
You should not worry adding small amounts of purified water with pH 5.
It will simply NOT AFFECT significantly the pH of your tank water.


Small amounts don't. That is true. However, my wavemaker causes a lot of
evaporation, so I have to add water to the tank daily.

- you do not need to process ro
water either... Acid pH level of RO water is not important!


If that is the case, you won't mind if I pour a bottle of HCL into your
aquarium, since pH is not important to you.


Wrong. Adding purified water at pH 5 IS NOT THE SAME as adding
a bottle of HCl to your fish tank...


I know. I was being a smartass.

And you should know it better.
I would not mind to pour purified water (without CO2) with a *small*
addition of HCl to cause *same pH 5 of the water*. That is correct:
I wouldn't mind!
The single serious mistake in your thinking process is that you seem to
miss the fact that it takes VERY LITTLE of acid to drop pH of pure water
(pure = without any buffers in it...) Based on this mistake the rest of
conclusions is wrong, too.

This is incorrect. The RO water I tested for pH was in an unsealed five
gallon plastic container, and had been made at least four days before I
tested it. The pH was 5.0, indicating high concentrations of CO2 in the
water. Once I add buffers and aerated the water, the pH rose to 7.5.


It did not indicate "high concentrations of CO2"! (high/low is very vague
anyway...)
See, this is exactly what takes you off track here...
High buffering capacity of water means it is hard to CHANGE pH of water
with addition of acid. Low buffering capacity of water means it is very
easy to change pH of water with even very small addition of acid (like CO2).


Point taken. I guess where I got this all mixed up was the fact that I never had
to worry about low pH in my take up water before, because I used DI water.

If you do not believe me, try to challenge yourself with calculation of
HOW MUCH CO2 does it take to change pH of purified water (18Mohms) from 7 to
5.
I asure you, it does not take much CO2 to make significant drop in pH
assuming there is no buffers in the water. In fact, by adding buffers to the
water you probably DID NOT CHANGE THE AMOUNT OF DILUTED CO2 in the bucket...
So pouring the bucket with or without buffers you actually add THE SAME amount
of CO2 into your tank. The buffer just makes you feel better, you see pH 8 :-)


I also aerated the water, which should help drive off the CO2. Right? By the
way, I just made up a new batch of RO water today, and it tested below 4.5 (the
lowest range of my test kit).

After several hours in the bucket the water will have NORMAL
level of CO2 and other gases (Nitrogen, Oxygen) dissolved in it.


Wrong, wrong, wrong. Make up a gallon of RO water, test the pH, then leave
the water in an unsealed plastic container for four days, and then test the
pH again. Then come back and tell me that the pH has stabilized to an
acceptable reading (5.0, in my case, is not acceptable, and since the pH was
at 5.0 after four days, I can imagine what the pH level was at one day. I
plan to find out tonight).


After couple of hours of aerating, the level of CO2 in solution will reach
equilibrium with the ambient CO2 levels.


With aeration, yes.

The same will happen with oxygen and
nitrogen. This *very small* amount of CO2 will always cause significant pH
drop
in water lacking buffers, but this effect should not worry us, tank keepers!
There is simply nothing in the water to neutralize acidity of dissolved CO2
- oxygen or nitrogen solutions are neutral and they do not cause any pH shift.


Doesn't calcium react with CO2 in solution to form calcium carbonate (CaCO3)?
Yes, it sure does. Of course, any CO2 sequestered this way will only be
replaced by CO2 from the atmosphere. Correct?

I'm sure it is able to support higher calcium levels. The thing is that all
marine reef tanks use up calcium so it has to be added. I hadn't added any
calcium since my last partial water change (about a month). That is why the
calcium levels were low. I had been adding buffer periodically, however,
which is why I was suprised that my pH was only 7.5. I have a wave maker
which causes a lot of evaporation, so I have to add makeup water frequently.
This is why I am convinced that the unbuffered RO water was the culprit.


And this was my point - you just need to increase dosage of buffers&calcium
into your tank due to the animals activity and NOT due to the effects you have
discribed ("diluting your buffers with RO water containing a lot of CO2").
You want to add buffers to ro-water before adding it to the tank? Fine...
But this is not important. The same effect you would achieve adding buffers
directly to the tank. The dosage of buffers and calcium should be related
to the uptake of animals/plants/algae you keep in your tank and NOT related to
the pH or amount of water you use to top-off the tank to replace what has
evaporated.


Point taken. However, there is a direct relationship between alkalinity and pH.
And it makes sense to me to add the buffer to the make up water instead of
putting it directly into the tank.

I only add enough clacium to the RO water to make it the same as my tap
water, which is 60 mg/L, not enough to cause precipitation since even at that
level, adding it to the tank water (which has a concentration of 280 mg/L) is
still diluting the tank water. After a couple of days, I will check the
calcium concentration in the tank water to see if addition calcium is needed.


As I said before, switch your focus from the bogus effects of "diluting"
your buffers to REAL effects of animals uptake of buffers/calcium...
Adding RO water just REPLACES WHAT HAS EVAPORATED. It does not affect
significantly anything else in your tank in comparison to animals uptake.



And if you test the tank water, and find that the Calcium, alkalinity and pH are
off before you add unbuffered water, low pH water?

Why would my tank water not support high calcium levels? The only reason for
the levels to drop in the first place is because the animals and macroalgae
in the tanks are using it. That is why you have to add calcium periodically
to reef tanks. I have 4 inches of aragonite sea sand in the tank and three
inches of it in the refugium, so the pH isn't going to fall below about 7.5.


So why do you worry about minuscule levels of CO2 in your RO water?


Because I saw a notable drop in the pH of my tank after I introduced the RO
water. That was the reason for my concern in the first place, and why I
investigated the pH of the RO water.

Do not experiment unless you are sure what you are doing
(i.e. have good background of basic chemistry courses).


See above. Ok Einstein, what is the vapor pressure of CO2? Note. I've had
reef tanks for 14 years (but have only used RO for the last two years), have
a maroon clown fish that is also 14 years old, have a 1,200 gallon garden
pond, and have raised tropical fish since I was 11 years old. I am also a
geologist (more specifically, a hydrogeologist).


Well- true, I am not Einstein - in fact, I do not even have a degree in
chemistry.
So I should probably shut up and wait for you to easily figure out how much
CO2 does it take to lover pH of purified water from 7 to 5... Then you can
compare how much CO2 does it take to drive normal sea water to pH 5...
Please do yourself a favor and present these calculations.

The problem is NOT the tank water. The problem IS the make up water.


Ok... your are wrong. But I am not going to continue this thread.
I understand you invested too much in this discussion and it will be hard for
you
now to admit you made a mistake... Especially after you were throwing your
degree
at us here and years of fish keeping experience...
So I will shut up now and leave you alone. Your tank - your problem... :-)

Maybe in the last act of desperation I will suggest following reading:
http://www.advancedaquarist.com/issues/may2002/chem.htm
There are some charts in this article - try to match amount of CO2
which will cause pH drop to 5 in water having 0 buffering capacity.


Thanks for the link. I'll get back to you. I'm running some more tests.


  #8  
Old April 19th 05, 02:34 PM
Pszemol
external usenet poster
 
Posts: n/a
Default

"George" wrote in message news:[email protected]_s21...
- it does NOT take a lot of CO2 to lower pH of purified water with no buffers,
in fact, it takes VERY LITTLE CO2 to change pH, due to the lack of buffers.


No comment on above?? ;-)

- it does not *dilute* buffers, it rather brings them BACK to the level
before water evaporated leaving higher concentration of buffers there.


Please explain how water with no buffers can bring water with buffers "BACK to
the level before water evaporated leaving higher concentration of buffers
there". My sal****er was already depleted of buffer before I added the RO water
(as indicated by the low pH - 7.5 as opposed to 8.4). If the purified water
with no buffer has a low pH due to its CO2 content, adding this low pH water to
the salt water will in fact deplete the buffer in that sal****er because it will
use up however much buffer it takes to neutralize the CO2.


You are partially right, but not the ro water is the problem here...
Actually in terms of buffers you do not care about dilutions
- if your water has buffering capabilities to neutralize addition
of 1 mol of HCl before top off then after adding even additional 10%
of pure water it will STILL HAVE CAPABILITIES TO NEUTRALIZE same amount
of acid. When you have not enough buffer for your animals then you have
not enough buffer, period. Adding pure water does not decrease or increase
your total tank buffering capabilities.

When water evaporates it does not take with it your buffers,


No it does not. What takes the buffers is CO2, which is added to the
water by micro/macroalgae at night, and by the animals in the aquarium.


CO2 is only part of the problem here. And as you noticed yourself now,
the problem is in your tank water, not your top-off purified water...
Totaly opposite to what you were arguing before.

So the problem is NOT in your top-off purified water - that is for sure...
If you had alk level 10, then you let 10 gallons of water to evaporate and
then you add 10 gallons of purified water you will be back to ~10 alk level.


Unless something else, such as the plants and animals in the tank are using up
the buffer, which we've established that they do.


So, once again, the problem is not related to your top off water with pH 5.

Small amounts don't. That is true. However, my wavemaker causes a lot of
evaporation, so I have to add water to the tank daily.


Mee too. It still does not make any difference!
CO2 freely dissolves in your tank water exactly as in your ro water.
The difference is in the buffers: you do not have them in the ro-water
so that is why you see pH drop.

See, this is exactly what takes you off track here...
High buffering capacity of water means it is hard to CHANGE pH of water
with addition of acid. Low buffering capacity of water means it is very
easy to change pH of water with even very small addition of acid (like CO2).


Point taken. I guess where I got this all mixed up was the fact that I never had
to worry about low pH in my take up water before, because I used DI water.


And this is another strange thing in your description.
DI water SHOULD have the same issues as RO or distilled water.
Real DI water should be even cleaner than RO water, so it should
be even more easy to change its pH with CO2 introduction...
If you never noticed low pH of your DI water I would bet it was
not very pure water...

I also aerated the water, which should help drive off the CO2. Right?


Yes. But if you have a lot of CO2 in your indoor air (humans, pets, etc)
the equilibrium after aerating will be on the higher levels of CO2 in the
water, which translates to lower pH levels of the pure water.

By the way, I just made up a new batch of RO water today, and it
tested below 4.5 (the lowest range of my test kit).


And this does not surprise me. What I do not understand is why
do you even bother measuring pH level of purified water...
It is completely irrelevant to our situation.
The pH of mixed salt water before a water change is a totally
different story and you need to measure it for sure...
But RO water? Forget it. DI water? Forget it. Distilled ? The same.
All these water types will always have low pH readings when after
being in contact with air containing CO2. This is a fact of life.

After couple of hours of aerating, the level of CO2 in solution will reach
equilibrium with the ambient CO2 levels.


With aeration, yes.


Without aeration the same. But it just take a little longer.
As long as you have water/air surface contact the gases will diffuse
and will exchange between water and air... Plain and simple physics.

Doesn't calcium react with CO2 in solution to form calcium carbonate (CaCO3)?
Yes, it sure does. Of course, any CO2 sequestered this way will only be
replaced by CO2 from the atmosphere. Correct?


You do not want this process to occur. This is the snowy precipitation
of calcium from the solution. When you see this something bad happened
to your water. You need to do everything to prevent this from happening.

Point taken. However, there is a direct relationship between alkalinity and pH.
And it makes sense to me to add the buffer to the make up water instead of
putting it directly into the tank.


It really does not matter. The way I put the buffer is I dissolve
a tablespoon of buffer powder in luke warm cup of purified water
and add the solution directly to the tank, in the high velocity spot,
usually into the outlet of the return water from the sump...
The point is that you not need to worry about pH of pure water.
If you like it better to add buffer to top off water - do it...
But don't you tell me you do it "because this water has scarry
pH level 5"... You do it because you do not have enough buffer
IN YOUR TANK WATER due to the living processes taking part in it.
Addition of CO2 to your system with top-off water is so small
that any pH fluctuations of pH after top-off would be worrying.
You need MUCH MOOOOORE buffering capacity in your tank than
it is needed to buffer small addition of CO2 from ambient air.
You will see details after you read the article by Mr. Randy Holmes.

And if you test the tank water, and find that the Calcium, alkalinity
and pH are off before you add unbuffered water, low pH water?


Again, it really does not matter.

So why do you worry about minuscule levels of CO2 in your RO water?


Because I saw a notable drop in the pH of my tank after I introduced the RO
water. That was the reason for my concern in the first place, and why I
investigated the pH of the RO water.


Very interesting. How much water you have added and how fast?
Did you take measurements just before adding water and just after?
What is your normal error of pH measurement and what pH change
you call "notable drop"? I would guess you need to do a massive
top off and do it very fast to notice any influence of CO2 on pH.

Maybe in the last act of desperation I will suggest following reading:
http://www.advancedaquarist.com/issues/may2002/chem.htm
There are some charts in this article - try to match amount of CO2
which will cause pH drop to 5 in water having 0 buffering capacity.


Thanks for the link. I'll get back to you. I'm running some more tests.


Calcium level of 280 and pH 7.5 is worrying. What salt mix do you use?

BTW - To really know your pH changes you need to replace your color pH
tests with electronic pH-meter and make sure it is correctly calibrated...
I am using one and had been using color test - I am speaking from experience.
Of course, pH-meter is not good for directly testing pH of ro/di/distiled water.
  #9  
Old April 19th 05, 04:03 PM
George
external usenet poster
 
Posts: n/a
Default


"Pszemol" wrote in message
...
"George" wrote in message
news:[email protected]_s21...
- it does NOT take a lot of CO2 to lower pH of purified water with no
buffers,
in fact, it takes VERY LITTLE CO2 to change pH, due to the lack of buffers.


No comment on above?? ;-)

- it does not *dilute* buffers, it rather brings them BACK to the level
before water evaporated leaving higher concentration of buffers there.


Please explain how water with no buffers can bring water with buffers "BACK
to the level before water evaporated leaving higher concentration of buffers
there". My sal****er was already depleted of buffer before I added the RO
water (as indicated by the low pH - 7.5 as opposed to 8.4). If the purified
water with no buffer has a low pH due to its CO2 content, adding this low pH
water to the salt water will in fact deplete the buffer in that sal****er
because it will use up however much buffer it takes to neutralize the CO2.


You are partially right, but not the ro water is the problem here...
Actually in terms of buffers you do not care about dilutions
- if your water has buffering capabilities to neutralize addition
of 1 mol of HCl before top off then after adding even additional 10%
of pure water it will STILL HAVE CAPABILITIES TO NEUTRALIZE same amount
of acid. When you have not enough buffer for your animals then you have
not enough buffer, period. Adding pure water does not decrease or increase
your total tank buffering capabilities.

When water evaporates it does not take with it your buffers,


No it does not. What takes the buffers is CO2, which is added to the
water by micro/macroalgae at night, and by the animals in the aquarium.


CO2 is only part of the problem here. And as you noticed yourself now,
the problem is in your tank water, not your top-off purified water...
Totaly opposite to what you were arguing before.

So the problem is NOT in your top-off purified water - that is for sure...
If you had alk level 10, then you let 10 gallons of water to evaporate and
then you add 10 gallons of purified water you will be back to ~10 alk
level.


Unless something else, such as the plants and animals in the tank are using
up the buffer, which we've established that they do.


So, once again, the problem is not related to your top off water with pH 5.

Small amounts don't. That is true. However, my wavemaker causes a lot of
evaporation, so I have to add water to the tank daily.


Mee too. It still does not make any difference!
CO2 freely dissolves in your tank water exactly as in your ro water.
The difference is in the buffers: you do not have them in the ro-water
so that is why you see pH drop.
See, this is exactly what takes you off track here...
High buffering capacity of water means it is hard to CHANGE pH of water
with addition of acid. Low buffering capacity of water means it is very
easy to change pH of water with even very small addition of acid (like CO2).


Point taken. I guess where I got this all mixed up was the fact that I never
had to worry about low pH in my take up water before, because I used DI
water.


And this is another strange thing in your description.
DI water SHOULD have the same issues as RO or distilled water.
Real DI water should be even cleaner than RO water, so it should
be even more easy to change its pH with CO2 introduction...
If you never noticed low pH of your DI water I would bet it was not very pure
water...


DI resins remove dissolved gases like CO2, so you shouldn't see the same level
of pH drop you see with RO. That was my point.

I also aerated the water, which should help drive off the CO2. Right?


Yes. But if you have a lot of CO2 in your indoor air (humans, pets, etc)
the equilibrium after aerating will be on the higher levels of CO2 in the
water, which translates to lower pH levels of the pure water.


Not much I could do about that, since my tank is in the basement.

By the way, I just made up a new batch of RO water today, and it
tested below 4.5 (the lowest range of my test kit).


And this does not surprise me. What I do not understand is why
do you even bother measuring pH level of purified water...


Sigh. Because I didn't realize that RO membranes allowed CO2 to pass through.
CO2 not only lowers pH, but promotes algae growth. When I saw the low pH levels
in my tank (which, in 14 years of running, I've seen it maybe twice), I decided
to test the make up water.

It is completely irrelevant to our situation.
The pH of mixed salt water before a water change is a totally
different story and you need to measure it for sure...
But RO water? Forget it. DI water? Forget it. Distilled ? The same.
All these water types will always have low pH readings when after
being in contact with air containing CO2. This is a fact of life.

After couple of hours of aerating, the level of CO2 in solution will reach
equilibrium with the ambient CO2 levels.


With aeration, yes.


Without aeration the same. But it just take a little longer.


Well, after four days with no aeration, the pH was 5.0. That bothers me, if for
no other reason than it makes me wonder what the CO2 levels are in my basement.

As long as you have water/air surface contact the gases will diffuse
and will exchange between water and air... Plain and simple physics.

Doesn't calcium react with CO2 in solution to form calcium carbonate (CaCO3)?
Yes, it sure does. Of course, any CO2 sequestered this way will only be
replaced by CO2 from the atmosphere. Correct?


You do not want this process to occur. This is the snowy precipitation
of calcium from the solution. When you see this something bad happened
to your water. You need to do everything to prevent this from happening.


I know that. I've never had that problem. I don't let my calicum levels get
that high.

Point taken. However, there is a direct relationship between alkalinity and
pH. And it makes sense to me to add the buffer to the make up water instead
of putting it directly into the tank.


It really does not matter. The way I put the buffer is I dissolve
a tablespoon of buffer powder in luke warm cup of purified water
and add the solution directly to the tank, in the high velocity spot, usually
into the outlet of the return water from the sump...
The point is that you not need to worry about pH of pure water.
If you like it better to add buffer to top off water - do it...
But don't you tell me you do it "because this water has scarry
pH level 5"... You do it because you do not have enough buffer
IN YOUR TANK WATER due to the living processes taking part in it.
Addition of CO2 to your system with top-off water is so small
that any pH fluctuations of pH after top-off would be worrying.
You need MUCH MOOOOORE buffering capacity in your tank than
it is needed to buffer small addition of CO2 from ambient air.
You will see details after you read the article by Mr. Randy Holmes.

And if you test the tank water, and find that the Calcium, alkalinity
and pH are off before you add unbuffered water, low pH water?


Again, it really does not matter.

So why do you worry about minuscule levels of CO2 in your RO water?


Because I saw a notable drop in the pH of my tank after I introduced the RO
water. That was the reason for my concern in the first place, and why I
investigated the pH of the RO water.


Very interesting. How much water you have added and how fast?


I added a couple of gallons over the course of a day during the weekend to a 55
gallon tank with an 18 gallon refugium.

Did you take measurements just before adding water and just after?
What is your normal error of pH measurement and what pH change
you call "notable drop"? I would guess you need to do a massive
top off and do it very fast to notice any influence of CO2 on pH.


The pH went from 8.2 to 7.5. I measured the pH before I added the water,then
after, well about two hours after.

Maybe in the last act of desperation I will suggest following reading:
http://www.advancedaquarist.com/issues/may2002/chem.htm
There are some charts in this article - try to match amount of CO2
which will cause pH drop to 5 in water having 0 buffering capacity.


Thanks for the link. I'll get back to you. I'm running some more tests.


Calcium level of 280 and pH 7.5 is worrying. What salt mix do you use?


Instant Ocean. I've always used this brand.

BTW - To really know your pH changes you need to replace your color pH
tests with electronic pH-meter and make sure it is correctly calibrated...


Yeah, I'll do that as soon as I pay off my car! I used to have access to a
really good probe when I worked at an Environmental Engineering firm here in
town. But since I've been working at another firm out of town, I don't have
that access (this firm doesn't have as much equiptment as the other one did).

I am using one and had been using color test - I am speaking from experience.
Of course, pH-meter is not good for directly testing pH of ro/di/distiled
water.



  #10  
Old April 19th 05, 08:10 PM
Pszemol
external usenet poster
 
Posts: n/a
Default

"George" wrote in message news:[email protected]_s21...
And this is another strange thing in your description.
DI water SHOULD have the same issues as RO or distilled water.
Real DI water should be even cleaner than RO water, so it should
be even more easy to change its pH with CO2 introduction...
If you never noticed low pH of your DI water I would bet it was not very pure
water...


DI resins remove dissolved gases like CO2, so you shouldn't see
the same level of pH drop you see with RO. That was my point.


After couple of hours of aeration the concentration of CO2 in the
water will be in equilibrium, regardless of the water origins...
DI or RO water should have the same pH at this point, if equally pure.
DI water tends to be cleaner than an average RO water, so the pH
of DI water would be lower than pH of RO water, but - again - it does
not matter at all.

Yes. But if you have a lot of CO2 in your indoor air (humans, pets, etc)
the equilibrium after aerating will be on the higher levels of CO2 in the
water, which translates to lower pH levels of the pure water.


Not much I could do about that, since my tank is in the basement.


And this could be the most important reason for your low pH 7.5.
High concentration of CO2 in the ambient air will cause high
concentration of CO2 in the tank water. To increase ventilation
of the fish room is the only way to cope with this issue...
The same high concentration of CO2 causes problems in my tank.

Sigh. Because I didn't realize that RO membranes allowed CO2 to pass through.
CO2 not only lowers pH, but promotes algae growth. When I saw the low pH levels
in my tank (which, in 14 years of running, I've seen it maybe twice), I decided
to test the make up water.


I do not care how much CO2 does RO stop/pass - since I am not using
RO water right from the filter but aerate it in an open bucket...

After couple of hours of aerating, the level of CO2 in solution will reach
equilibrium with the ambient CO2 levels.

With aeration, yes.


Without aeration the same. But it just take a little longer.


Well, after four days with no aeration, the pH was 5.0. That bothers me, if for
no other reason than it makes me wonder what the CO2 levels are in my basement.


You can simply find out using some CO2 meter - like this one:
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=4374263171
You could even think of running automated ventilation system
based on your CO2 level in the basement air :-)
Of course it would influence your whole house ventilation as well.

Yeah, I'll do that as soon as I pay off my car! I used to have access to a
really good probe when I worked at an Environmental Engineering firm here in
town. But since I've been working at another firm out of town, I don't have
that access (this firm doesn't have as much equiptment as the other one did).


You do not need state of the art meter... $50 one would be fine.
I got some used one from eBay made by Thermo Orion about 10 years ago.
Excellent condition, fully automatic, two channels (if you like to
monitor ORP levels as well) fluorescent blue display nicely visible
at night, AC powered - highly recommend: Thermo Orion 525A.

Good luck with your tank. Keep us posted how is it going with pH...
 




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