Originally Posted by krap101
You can't overfilter, but the increased flow could stress out your fish. Normally people go for around 10 turnovers/hour, and less with a canister.
That number is a little high. More realistically a filtration rate of ~5 times the volume of the tank per hour is where you want to be. An example is the Tetra Whisper 60 HOB
style filter that comes with many 55g kits. It has a max flow rate of about 330 GPH
and that's about 6 cycles per hour. I've found that to be very good for a 55g tank. I've got two of them on my 100g tank (5ft long) and it sufficiently filters the tank. Maybe a little too much for what my discus would like.