In article %lSkb.133058$9l5.75820@pd7tw2no,
Rick wrote:

the filter is a matter of choice. I'm running a Fluval 404 in my 77g.

I started with an impeller/reservoir/charcoal filter together with an
undergravel filter in a 55 gallon tank. I recently switched to a Fluval
304, but when I did, I turned off the undergravel filter, and almost
killed my fish because it seems they were starving for O2. I turned on
the UG and dropped an airstone in. I didn't consider that the fluval
filter was a completely closed system and doesn't aerate the water.

Fish are doing ok now but I don't think I've improved my tank much,
since I'm still running an UG filter, and I still have an annoyingly
loud pump. I do like the fluval, but I really want to get rid of this
pump. (Can you recommend an air pump that's truly quiet?) (Why do I
have to import O2 anyway?)