PH control with CO2

[nycman]

I have a large planted tank 200G with overflow and sump. After several tweaks on the plumbing, I have virtually no surface agitation and ability to overdose on CO2 (based on my history with this tank, a good thing). I am getting Discus and want to be more careful with the daily PH swings. I run the CO2 8 hours a day inside of a 10 hour lighting period. Without the PH controller, my PH would peak at 7 (my tap water PH) just before the CO2 would come back on, and then during the 8 hour CO2 cycle dip to upper 5 or lower 6, depending on my bubble count tweaks.

Here is my question on setting up my controller...with domestically bred Discus, should I:

1) run my CO2 24 hours a day with the controller auto shutting it on and targeting a specific PH - I have tested it and can keep it very stable at 6.3 to 6.5, and still get ample CO2 into the tank. This way the PH of the tank will be at this value 24x7 as I will be running the CO2 at night as needed for this PH.

2) run it on the 10 hour lighting cycle, shutting it off at night and allowing the PH to creep back up to 6.8 or 7. This way the daily PH fluctuation will be 6.3 or 6.5 to 6.8 or 7, not insignificant, but not huge.

Assuming both approaches are equally appropriate for the plants - which is better for the Discus?

[Ryan925]

I would be concerned about o2 levels at night with co2 running and no photosynthesis going on

[nycman]

Good point. I can get an ORP probe and shut off CO2 at night automatically if ORP drops too far.

[Filip]

I would definitely go for the first option Steve.
I would also most certainly add an good surface agitation to enrich the water with oxigen too .
O2 and Co2 presence in the water column do not exclude each other , and the best way is to have plenty of both . You'll end up pumping / loosing more co2 to achieve that , but its a small trade off for keeping beautiful discus planted tank .

Youll have to figure out a safe way for changing water too . I guess smaller and more frequent WCs will prevent big pH swings during the WC's .

[nycman]

Thank you. Will set it up then for 24x7 CO2 injection. My overflow is a reef savvy ghost that has about 18 inches of surface agitation. I am plumbed for 10% automatic water changes. Thanks for the advice.

[nikolyator]

Takashi Amano never ran C02 at night. "it is rude to run C02 at night" that's what he said about. give a break for fish at night. let it breath. read some different sources about. read what Tom Barr think and explain about it. Ph swing with co2 doesn't harm to fish. KH does. ph in my tank at night 8.07 and at photoperiod 6.6-6.7. just try to give more oxygen to the water. lets say with wet dry filter. again, it's only my opinion. 🙂

[Filip]

Takashi Amano never ran C02 at night. "it is rude to run C02 at night" that's what he said about. give a break for fish at night. let it breath. read some different sources about. read what Tom Barr think and explain about it. Ph swing with co2 doesn't harm to fish. KH does. ph in my tank at night 8.07 and at photoperiod 6.6-6.7. just try to give more oxygen to the water. lets say with wet dry filter. again, it's only my opinion. ��

Amano and Barr are plant and scape specialists and their advices are mainly biased towards an optimal plant growth . I would't lean on their references for discus keeping , because discus keeping is completely deferent ball game from the planted tanks .
Your PH changes of almost 1.5 degrees on a daily level is not a good fish keeping practise for every fish in general and let alone for discus .
Fish and especially discus require stable parameters to thrive and PH is no exception .