I was getting a few bubbles out of the 20" Cerges with the Rio 2500 even though there was more than 10' of PVC to the spraybar but now no bubbles even though the Cerges is nearly directly underneath the bulkhead going to the tank from the sump. No idea how that could be but it is. Rio 2500 is supposed to have 530 gph at 4' head. I count 4 90* elbows including the ones in the reactor itself so the pump might be producing 400 gph through the Cerges. http://reefcentral.com/calc/hlc2.php
Putting a reactor on the return will cut its gph right there. The Rio was keeping 2 U tubes full when I just had the CO2 line stuck in the pump's intake but when I put the Cerges on the second U tube kept getting bubbles in it due to flow that wasn't quite adequate.