If you have a reef ready tank with overflows, you need to raise the level of water in the overflows, as the waterfall effect loses a ton of c02. This will help a lot. Use a Durso standpipe or extend the current pipe in the overflow so it is taller and no more than 2-3 inches from the water line. I raised mine from 6' to 1.5' and it is much quieter and the c02 loss is much less.

Please look for my threads on a 180 gal over the last couple weeks, as many have given me good advice for my setup.

I raised the level in the overflows, got better current and flow thru, used the venturi idea mentioned above (not the Mazei), covered the sump, etc.

All have increased my c02 assimilation.

Direct the flow from your reactor into the intake side of the pump to the tank. That will help distribute the c02.

Current also plays a significant factor.

Hope this helps.