CO2 injection rate for a 4' x 2' x 2' tank

[nivlekx]

No coral chips. Just a normal gravel above 2 bags (which is way way less than the recommended amount) of JBL substrate. I have no idea why this happens. Maybe its the ceramic rings, not too sure.

[PeterGwee]

I do suspect it is your substrate (coral chip stuff inside)...if not I don't see why your KH kept increasing with CO2 injection. Another possible thing is your KH test kit is bad?...OK, do a KH test but fill the sample to the 10ml mark if the original test ask for 5ml..then count the number of drops..then divide by 2 to obtain a more precise KH value.

[David]

do you happen to have rock deco? it may have lime composition in them that is increasing your KH. It may be a good idea to check your tap water KH as well.

[nivlekx]

Just measured today, KH 5, pH 7.7 under consistent CO2 injection. I think the chart doesnt hold in my tank. Its simply not possible. I do have rocks in my tank so I suppose thats contributing to my problems. BBA is starting to grow, I suspect due to excessive CO2. Any advice.

[bclee]

In most cases, when charts don't hold, the KH reading from your test kit is higher than the actual HCO3-. This is due to buffers other than carbonates contributing to the KH reading.

That means CO2 level from KH/pH measure will usually reads higher that what it actually is. It very seldom happen as in your scenerio.

I seriously think that you are not getting enough CO2 into your tank. BBA will grow when there is lack of CO2 not excess.

BC

[wks]

nivlekx, try the elimination method. Stop all addition of chemicals to your tank, including liquid fertilizer. Record your CO2 supply(get a bubble counter), test your tank water parameters first, then take out all rocks. After a few days, check CO2 supply again and test water parameters.
If pH drops significantly without any drop in CO2 supply, the rocks are contributing to the kH.
If CO2 bubble rate drops, check your needle valve.
If nothing changes, your substrate has coral chips, thus contributing to high kH.

[bclee]

I think KH is not much a concern now. KH 5 is OK.

I think the problem may be the CO2 set up. At KH 5, with good CO2 level, you should get a pH of about 6.8.

Look at your CO2 injection. Then the source of KH increase. BTW, your KH level isn't really that bad.

BC