help me some one please

[Alien Anna]

I don't thin the levels of CO2 had something to do with this. Unline on land, o2 and co2 doesnt displace each other in water. I looks like it is fixed, but i just wanted to cleaar this up.

The real issue is that CO2 can cause a pH crash in your tank, which could result in the symptoms you observed, not that CO2 can somehow displace O2 in the water.