Reducing PH with CO2
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Reducing PH with CO2

This is a discussion on Reducing PH with CO2 within the Beginner Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; --> Hi all, I have an aquarium with a pair of kribensis. My PH is around 8. Now I need the ph to go down ...

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Old 08-25-2010, 08:14 AM   #1
 
Reducing PH with CO2

Hi all,

I have an aquarium with a pair of kribensis. My PH is around 8. Now I need the ph to go down to 7. I do weekly 20% water change and the tap water PH is around 8. If i add CO2 to the aquarium pumping in 1 bubble per 5 seconds would the PH go down? Also that 20% water change with PH 8 would it effect the aquarium PH?

Should i use Seachem Regulator or would refrain from using it because of phosphate and since i have low light plants (15W for 60 Litres tank and 10 hours daily with lights on) algae will start forming?


Thanks in advance
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Old 08-25-2010, 06:15 PM   #2
 
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it seems peat or ada soil will lower ph too.
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Old 08-25-2010, 06:17 PM   #3
 
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In most cases, the aquarist balances KH (which raises pH) with CO2 (which lowers pH). For example, we are blessed with soft tap water, both in terms of KH and GH. We add sodium bicarbonate (NaHCO3, baking soda) to get 4 degrees of carbonate hardness (4 dKH) as measured with a Tetra KH test kit (inexpensive but effective). With a typical equilibrium dissolved CO2 level of 2-3 mg/l, this gives us a "natural" pH of around 7.7. We then inject CO2 to lower the pH to 6.9, giving us a dissolved CO2 level of 15 mg/l, which is just about perfect.
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Old 08-25-2010, 06:19 PM   #4
 
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CO2 means Carbon Dioxide, a gas present in air which dissolves promptly in water

CO2(g) + H2O(aq) ---> H2CO3(aq)

to form H2CO3 or Carbonic Acid. Like other acids, H2CO3 dissociates in aqueous media to gives HYDROGEN IONs (e.g. H+)

H2CO3(aq) ---> HCO3-(aq) + H+(aq)

Then, H2CO3 plays like an acid and it increases |H+|, it diminutes pH levels.

B)Use a formula to explain how a lower pH would affect the CO3-- in the ocean..

CO3-- is known like Carbonate Ions which may dissolve in water. Carbonate ions come from Carbonic Acid by its acidic dissociation

CO3--(aq) + H+(aq) ---> HCO3-(aq)
HCO3-(aq) + H+(aq) ---> H2CO3(aq) ---> CO2(g) + H2O(aq)

so ACIDITY MAY CONVERT CO3-- IN HCO3- TOWARD H2CO3/CO2.

C.)Assuming a fairly constant Ca2+ in the ocean, how would a change in CO3-- affect the calcification rate in a coral reef?

Corals are oceanic animals able to form large clusters based on Calcium Carbonate. This matter is slightly soluble in water because it obeys by this equation

Ksp = 6E-9 = |Ca++| * |CO3--|

This Mathematics states that IF |Ca++| AND |CO3--| REACH OR OVERTHROWS THE HIGHLIGHTED PRODUCT, THEN CaCO3 MAY EXIST IN WATER MEDIA.
Since the previous is a constant value determined by chemists at defined temperature level T=25 C, you understand that THE GREATER |CO3--| AND THE EASIER THE CaCO3 FORMING.
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Old 08-26-2010, 12:38 AM   #5
 
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Quote:
Originally Posted by migdem View Post
Hi all,

I have an aquarium with a pair of kribensis. My PH is around 8. Now I need the ph to go down to 7. I do weekly 20% water change and the tap water PH is around 8. If i add CO2 to the aquarium pumping in 1 bubble per 5 seconds would the PH go down? Also that 20% water change with PH 8 would it effect the aquarium PH?

Should i use Seachem Regulator or would refrain from using it because of phosphate and since i have low light plants (15W for 60 Litres tank and 10 hours daily with lights on) algae will start forming?


Thanks in advance
Kitten has answered you well on this topic, but for what's its worth I do not believe in using chemicals to adjust water parameters, nor CO2.

The better long-term solutio is to invest in a RO unit and mix RO water with tap water. O)nce you get the mix where you want it (in terms of pH and GH and KH) it will be easy enough to duplicate every water change. This is the only safe effective means of softening/acidifying water. Peat will work, but when you are trying to adjust it as much as you are, and starting with that hard a water, it will take a lot of peat and it wears out and needs to be replaced. Buying water is similarly more expensive long-term. Rain water will work, if you have enough and it is free of chemicals. Otherwise RO (reverse osmosis).

Seachem's Regulator will be expensive over time, and I'm not sure what is actually is, the info on the Seachem site doesn't say, only that it somehow precipitates calcium and magnesium. I personally would not go down that road (using chemicals or whatever this is).

A comment on using sodium bicarbonate (baking soda). "Sodium bicarbonate has no effective buffer action and cannot stabilize pH in the face of additional acidic waste products. Also, one must not continually add sodium bicarbonate to adjust the pH because eventually the sodium ions present will reach intolerable levels. ...We prefer to to adjust the pH in a more "natural" way by exchange with freshly prepared soft water [and they use RO as discussed earlier in the article]." From an article entitled "Maintaining Environmental Conditions Suitable for Tropical and Subtropical Forest-adapted Fishes (part 2), TFH July 1996. Authors are Dr. Stanley Weitzman, Lisa Palmer, Dr. Naercio Menezes and Dr. John Burns, all eminent scientists.

Using any of the methods other than water that is relatively "pure" such as RO or rainwater always carries several risks. Chemistry can suddenly change, and can spell death to the fish within hours if anything goes wrong.

Byron.
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