I recently got a new set up off craigslist. A 135 reef ready tank and stank for $200. I thought it was a pretty good deal. Anyways it also came with 2 emperor 400s and when I first started them they had pretty slow flow rate. A month later it was even slower. I mean the only thing that kept the biowheels moving was the spray bar. So I gave them a good cleaning amd turned them back on and it was about what it was when I first started them. I dont know why or if there is something maybe Ive done wrong. Its my first time with the emperor 400 and if this is how they operate it will surely be the last. Perhaps i should take into account that i dont know how old they are and what care was taken of them since i got them second hand, but its still making me mad. If anybody has any ideas as to what may be the issue then let me know!!!