My experience has been that it's easy to overwhelm the reactor. I started out thinking a high volume pump would process more water therefore giving me a lower bubble count and saving me $ on CO2. That hasn't proven out in reality. The fact in my case is that there's a sweet spot for these things and if you exceed it you're going to get bubbles in the tank. That sweet spot for me is about 100-120 gph. This is a 40b with a Fluval FX5 as the main filter. Lots of water movement, albeit diffused through 30" of spraybar, so there's no water in the tank that's sitting still. I'm pushing about 4-5 bps through the reactor giving me a full pH stop of saturation, making the drop checker lemon yellow by lights-out.