Join Date: Mar 2011
Location: Oregon State Beavers!
Every tank is going to be different even tanks of the same size. This is based upon on how well the CO2 is being diffused, the plant uptake, and any off gassing that is occurring due to surface agitation. Personally I feel it is safer to use a nice surface agitation (I have dual bio wheels) and just use more CO2 which is dirt cheap. The agitation insures that you are replenishing your oxygen levels which is obviously very important for your fish. The drop checker is a good idea and you can find them on the swap and shop including 4dKH solution for about 12 or so dollars. You can also get a relative idea based upon pH change. A 1.0 drop in pH is equal to ten times the CO2 concentration before the drop. However, not knowing the exact atmospheric CO2 concentration makes this an inexact science. It is typically between 2 and 3 ppm so a 1.0 drop will yield 20 to 30 ppm.
Your growth rate will always be your best indicator along with fish behavior. Fish fleeing to the surface for air is an immediate sign of too high of levels of CO2.