I was wondering if anyone knows a good starting point of how many bubbles per second I can run on my CO2 system. My tank is 75 gallon, heavily planted, ph 6.5, kh is in soft to slightly medium range and the only fish I have in there are oto cats and one siamese algae eater, along with 10 amano shrimp. I have a glass diffuser and my goal is to add as much co2 I can without causing fish stress.

If you know your exact Ph and Kh there are conversion tables to read actual CO2 concentration. This assumes that you don't have very hight levels of phosphate in your tank which obscure the KH/PH/CO2 relationship. Try here: Measuring CO2 levels in a Planted Tank

Generally you want 20-25ppm of Co2 maximum to avoid trouble with your fish. Make sure if the tank is heavily planted you have some way of giving your fish O2 at night otherwise you may wake up to find them at the top of the tank gasping for air.

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29 Gallon Planted
1 Angelfish; 2 German Blue Rams; 11 Rasbora Boraptensis; 3 Khuli Loaches, 1 BN Pleco

20 Gallon Planted
2 German Blue Rams; 5 Corydoras Paleatus; 4 Otocinclus Catfish; Amano Shrimp

5.5 Gallon
Betta, Some plants.

That table is almost useless unless you use DI water. The number of bubbles per second means nothing. If I add no CO2 but I have a kH of 4 and a pH of 7.0 does that mean I have good CO2? No, you still have 0. And according to my specs, I have 60ppm of CO2.

Every tank will be different due to how fast the CO2 is being used and several factors affect this: WPG, type of bulbs, how many plants, how fast growing, type of soil, nutrients being added, kH, surface tension, hours lights on, type of diffuser, GPH being moved, temperature...etc.

The easiest way to start out is to look for your pH to drop. See what it is before lights on and then see what is is at the end of the day. You should see a decent drop in pH if CO2 is in the tank. Now add more bubbles until you see fish acting funny or you see pearling. If you see the fish acting funny, back down on the bubbles per sec and increase your surface tension for a bit. If you see pearling this means the plants are maxed out and are giving off O2...this may not always happen depending on the tanks temp. This would be how you truly max out your tank....for now.

The reason I said for now is that this rate is not constant. As you get more fish, more plants, and the plants start to take off, you will probably be able to re-adjust your CO2 and nutrients to keep up.

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--->Pictures of my 75g Amazon tank<----

Thanks for your help. I have pearling, and so far the fish seem ok. I was having trouble with that chart based on the same reason you were saying. It could just be useless. For example what if I'm not adding any CO2...I would still have a KH and PH reading that could say that I have ??ppm. I'm going to go with eyeballing for now. I'm starting with 2 bubbles per second.