Discus and pH swings

[Tony F]

I recently introduced 4 discus into a heavily planted 120 gallon tank with pressurized CO2 injection. I have high lighting (4- 56 watt T5HO bulbs) suspended about 7 inch above the tank with lights on 10 hrs a day. My CO2 injection is controlled with a pH meter, so I can hold my pH steady @ 7.0 which equates to 30 ppm CO2. If I run my CO2 24/7 I can hold the pH steady within a +-0.1 tolerance. BUT, if I run my CO2 with lights on only, off with lights off, my pH raises to 7.5 - 7.6 during lights off. It slowly and steadily climbs during lights off. I turn the CO2 on 1 hr before lights on and it takes about 45 minutes for CO2 to build and pH to drop back to 7.0.

My dilemma is, should I run my CO2 system 24/7 or lights on only, so my question is how does the 0.5 - 0.6 daily swing in pH effect the fish? They have only been in the tank a few days, and are still adjusting to their new environment (and doing well), but I'm not sure about the pH swing and the well being / long term health of the fish. Cost of running the CO2 24/negligible, The issue is the health and well being of the fish. BTW, if it makes any difference I also have about 30 rummy nose tetras and 4 yoyo loaches (snail control) in the tank.

Looking forward to your thoughts and comments and hearing what others do with CO2 injection.

Thanks, Tony

[TURQ64]

My opinion is no harm on the .5 swing, but they are the judges, not me. I have .5 swings at times due to large water changes from storage barrels, and never see any bad effect..I don't have CO2, so I don't know if other parameters change...Gary

[BradC]

pH swings due to CO2 have no effect on fish.