I have a BRS Bio Pellet Reactor and at first i could not get it to work right, it seemed like it would work great for a few days then slowly get weaker & weaker, so i took a razor blade & ran in between the slits on the bottom of the cartridge ( made them a little bigger ) and now it runs great non stop it has been about a month a great tumbling. Now that it my Bio-Pelets but i think it might help with the carbon reactor. I just got the Carbon/GFO reactor ( same thing as Bio-Pellet ) and the only pump I had laying around was a Rio 600 the little guy. I am only running carbon and the majority of people say that you don't want your carbon to tumble, or just slightly. I have a 90G rimless and i used 9 Tbls of that BRS carbon and it seems like the flow is stronger on 1 side and lacking on the other, I think it is the same problem I had when I 1st tried a BRS reactor. Just throwing that out there would like to know if that helps or what.