My 2 # 4 hydors are currently working great on my 1 week old 150 gallon setup. They provide a nice wide range of strong current. Mine run 24/7. Probably looking to get one more. So far the best price I found and where I got all my supplies was premium aquatics @ $46 each for the # 4's. Find it cheaper, no problem they will match and thier customer service is fantastic and are very responsive and informative. I know the # 4's sell out quickly, had to wait a whole month for my second one.