I have a penguin 125 on my 15 gallon, and so far, it has been quiet (at least by my standards-to give you an idea I hate airpumps) The only noise mine makes is a constant trickle of water into the aquarium, a nice sound that masks the filter's noise. So far the biowheel has worked well, I don't have a undergravel filter and it alone is doing the job. The biowheel filters came highly recommended to me by a local angelfish breeder so according to my experience and his experience they are great!