Hi everyone,

Thank you for all the help in the past. My planted tank is doing well now and the growth is pretty good! As recommended I have purchased a solenoid and use a passive diffusion method. My tank is 2 x 1 x 1.5ft. I have 5 angel fish inside my tank.

I have set timers such that I have lighting for 6 hours a day together with the CO2 injection. When the light goes off, an air pump will turn on, reason being that I don't want to lose any fish due to too high a CO2 concentration/lack of oxygen as without light plant respire as well.

I noted that my tank has big PH swings, when the CO2 is being injected it can drop to 5 and when the the air pump is on it rises to 7.
So my questions are:-

1) Is this daily swings bad for my angelfish? I reduced the bubble count from 2 per second to 1 and it has reduced the drop in pH to 6 rather than 5.

2) Should I also remove the air pump totally? Will my fish suffocate to death? I am thinking that the aeration is causing dissolved CO2 to escape very rapidly causing a sudden swing in PH levels.

3) How can I make my pH more stable even with CO2 injection?