CO2 and pH

[Jen]

I just added CO2 to my tank last week. That is the only change to my tank.

Since adding it, I have done two water changes.

My tap water, and usually my tank water's pH is 7.4 or higher. Since adding the CO2, the pH has dropped to 6! maybe even lower. I am going to take a water sample to my fish store to be on the safe side.

I am worried about the drastic drop, and what it might be doing to my fish.

Any ideas on how to raise it, short of taking the CO2 off?

 

[Angry_Platy]

Have your fish been acting any different since the pH dropped....if not I wouldn't worry.

 

[iggy01]

Adding CO2 always causes the pH to drop a bit! But not usually that much..... unless you have high levels of CO2.

Do you know what the KH of your tank water is?

If your KH is below 3 you may need to raise it.

Good luck!

 

[Jen]

The kH is 4° I believe. I will test it again when I get home from work tonight.

 

[iggy01]

If your test kits are correct and you have a pH of 6 and a KH of 4 then you have way too much CO2.

Take a look at this chart for optimum levels.

Good luck!

 

[Jen]

I'm not quite sure how to read that. Normally my tap water is 7.4, so should I be looking for levels off that pH?

 

[iggy01]

If, before you added CO2 your pH was 7.4 and your KH was 4, it would give you a reading of 5 mg/l of CO2. Which I guess, is probably the reason you decided to add CO2. However, if you are saying your pH is now 6.0 and you were still to have a KH of 4, this would give you 133mg/l CO2 ( too much!).

You're not filtering over peat by any chance are you ? This could give you a false KH reading.

 

[Jen]

I never teste the kH before adding the CO2. I will test my tap water for that tonight as well.

My filtration is just a sleeve filled with carbon

 

[Jen]

I just tested my tap water, and its pH is 7.2, and the kH is 5°, which puts it around 10mg per litre of CO2.

My tank water is 6.2 pH and 5° kH, making the CO2 at 84mg/litre.

Does that make sence? what can i do to adjust it?

 

[iggy01]

The easiest way would be to ease back on the CO2. I know that's not what you wanted to hear. Another solution, could be to add an airstone to drive off some of the CO2. I'm not sure it would drive off that much CO2 though!

You said you were going to get your tank water tested. I think this would be a good idea, you never know..... one of your test kits may have gone faulty! This would obviously give a misleading reading on the CO2 chart.

This link and another may help you when your tank water has been tested.

Good luck!

 

[Jen]

I just added a conch shell to my tank under the advice from the plant guru at my lfs. My pH is now up to 7.0, and my kH is 3. things are looking better in the tank. Should I be happy with this, or is there anything else I can do?

 

[Nospherith]

get some calcium carbonates or magnesium carbonates and this will raise the level of the GH, general harness. GH is the buffering capacity for pH or something, which means that the more CaCO3 or MgCO3, the more carbonic acid your water will be able to absorb without lowering pH, so it's good that you got the crushed coral because that's a really good source of calcium carbonates. I'd say that whatever the CO2 level is, it's good. what diffusion method are you using?

 

[Jen]

I have one of these.

 

[simonbrown403]

When i first added a co2 system my tank readings where a little kayotic, it took it a few weeks to settle down, and for me to alter my routine to suit.

be carefull with using coral gravel to controle KH and PH, as the efects can be hard to prerdict and control, be sure to check PH every day.

try this site its got a real good tool for calculating co2 levels, go to bottom of page to down load to yr desktop. plus ull find loads of usfull info an plants, PH, KH and CO2 levels etc.

http/www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm

 

[sinistral]

get some calcium carbonates or magnesium carbonates and this will raise the level of the GH, general harness. GH is the buffering capacity for pH or something, which means that the more CaCO3 or MgCO3, the more carbonic acid your water will be able to absorb without lowering pH

Just one small point: While it's true that adding calcium or magnesium carbonate will raise GH, it is not correct that GH is the measurement of buffering capacity.

The measurement of buffering capacity in the aquarium is KH, or Carbonate Hardness as iggy01 was discussing. GH is a measurement of general hardness, which depends primarily on calcium and magnesium.

It's important to note this because adding calcium or magnesium carbonate will raise *both* GH and KH. Depending on the type of fish you have, this can either be a good or a bad thing.

I agree with simonbrown403-- in general adding things to your tank to treat numbers or readings can be a difficult thing. One thing we don't often consider is that changing water parameters can lead to a variety of different stresses, including osmotic stress.

I had thought that iggy's suggestion of easing back on the CO2 (by partially occluding the outflow) was a good one. One problem with DIY yeast driven CO2 rigs is that you can get a really variable output of CO2 from day 1 where you first put in a fresh batch of yeast and sugar and the yeast is pumping out the CO2 until day 20 (for example), where the yeast cells are dying in their own fermentation and are running out of substrate to convert to CO2. When this happens, the conditions that created the need for pH or KH adjustment are no longer the same, and the pH changes again...

As you've already added the conch and things are looking stable, it looks like you may be resigned to daily monitoring of water conditions and CO2 output until you get the routine that simon alluded to down Good luck, I'll be interested to hear how things turn out

EDIT: I just realized...I think I read in an old post that you have a commercial CO2 setup...this doesn't change the fact that it'll still be necessary to monitor how conditions are regularly in the tank, as yeast still dies and sugar runs out in commercial setups too...