Usually you branch off from pumps output with a T or manifold and give CO2 reactors line it’s own ball valve/return to tank so you can optimize the flow through it without effecting main pumps total output.
What size (dimensions) is tank and what is GPH rating of pump?
Example, for a 50gal tank, get a 400gph pump for 8x turnover rate. Then split pumps output to 3 returns to tank with a manifold and 3 ball valves, only one of those returns will will feed co2 reactor and its flow will be optimized for its specific needs. Probably 180gph going through reactor and then 110gph going to the other 2 tank returns.
6-8x turnover is my general rule but in a planted tank those outputs would be split up so that no return is over 180-200gph max. Don’t want plants blown sideways or big areas where fish are unable to swim around in tank because of high current. Usually around 100-180gph for each return in the tank seems the sweet spot. The bigger the tank the more returns you need for even current patterns/distribution around tank.
Last edited by DaveKS; 06-01-2020 at 03:07 PM.