CO², pH, and KH (Crushed Coral)

[stowcenter93]

Finally, I have my pressurized CO2 set up and running in my 29 Gallon tank. Got a well priced regulator for a 5lb tank. 

With a bubble rate of 3-4/sec after a week, I'm not noticing any change in my pH. I assumed this would be the case due to the large amount of crushed coral I used to buffer my system.

Are there any signs or tests I should be looking at to help me accurately dial this system in since pH shouldn't fluctuate that much due to my high KH?

[Mmiller2001]

The pH should drop regardless of KH. 

What is the pH (with injection) and what's the KH?

[Seattle_Aquarist]

Hi @stowcenter93

What is happening is this:

1)  The CO2 is making the water more acidic however the more acidic water is dissolving the coral (aka calcium carbonate) more quickly so the pH is remaining the same.  What is also happening is the dKH or the tank is increasing due to the dissolving of more coral.  Unless you are breeding livebearers I would remove the coral from the tank and run it without....many plants have trouble with higher pH and carbonate hardness (dKH). 

The way to accurately check your amount of CO2 would be using a 'drop checker' filled with 4.0 dKH indicator solution.  I like the Fluval CO2 Indicator Kit which comes with the indicator solution.  Be careful, increasing the amount of CO2 going into the tank without knowing the ppm of CO2 concentration can cause fish distress / death.  I run 30 ppm of CO2 or less in my tanks. 

Hope this helps! -Roy

[modified lung]

Agreed with @Seattle_Aquarist. CO2 up + pH same = KH is going up. Dissolving crushed coral would explain that.

[stowcenter93]

Thanks all. @Seattle_Aquarist, I do have a drop checker that has not turned green in a week yet at my current rate. It's rated as a 4 DKH solution.

Crushed coral removal is going to be a lost cause. It's too mixed in with my black fluval sand and, truth be told, I don't wanna do the work to remove that haha. My water is extremely hard but has no buffer. I would have pH swings alot and opted to add buffer to reduce problems, which worked for what I needed. 

If I am not seeing a change in my drop checker, nor signs of any stress in my fish, would the next logical step be to increase the rate of CO2 being injected slightly every 3-4 days until my drop checker responds with the desired green color?

Apologies if this formatting looks bad, I'm having issues with the forum on mobile. 

@Seattle_Aquarist

[Seattle_Aquarist]

On 3/13/2022 at 3:15 PM, stowcenter93 said:

Thanks all. @Seattle_Aquarist, I do have a drop checker that has not turned green in a week yet at my current rate. It's rated as a 4 DKH solution.

Crushed coral removal is going to be a lost cause. It's too mixed in with my black fluval sand and, truth be told, I don't wanna do the work to remove that haha. My water is extremely hard but has no buffer. I would have pH swings alot and opted to add buffer to reduce problems, which worked for what I needed. 

If I am not seeing a change in my drop checker, nor signs of any stress in my fish, would the next logical step be to increase the rate of CO2 being injected slightly every 3-4 days until my drop checker responds with the desired green color?

Apologies if this formatting looks bad, I'm having issues with the forum on mobile. 

 

@Seattle_Aquarist

Hi @stowcenter93

I'm not sure that I have ever encountered 'hard water' which would indicate a lot of dissolved calcium and magnesium that also had a low dKH but I do believe you.  Here in Seattle we have very, very soft water since our water supply consists of reservoirs fed by snow melt in the mountains.  Many of the members in our club, if they decide to use calcium, but it into a media bag that they can add or remove from their filter as needed.

With the crushed coral mixed with your substrate you will likely never be able to reach pH@7.0 (neutral) or acidic tank water.  Regular, weekly 50% water changes will help keep the dKH and dGH from increasing to extreme levels.  No way of knowing if the indicator solution you received with the drop checker is 4.0 dKH or not but let's assume it is.

When I am adjusting my CO2 levels in a tank I do one (1) small adjustment per 24 hours.  I do the adjustment in the morning so I can watch the fish and make sure they are not breathing rapidly or hanging near the surface which would indicate I went too high in my adjustment.  If fish do show distress I add an airstone which will quickly increase the exchange of gases as the surface and lower the CO2 ppm level.

Are you running an airstone or sponge filter in your tank?  If so that may be what is hindering the increase of CO2 levels in you tank.  The more surface turbulence there is the more exchange of gas at the surface of the water and the quicker the loss of injected CO2.  Hope this helps! -Roy

 

[Mmiller2001]

Is the tank new?