If you don't like the sound of a waterfall, then stay away from the Aquaclears. I find their waterfall a nice feature, as the sound of a waterfall is peaceful.

I have 2 AC110s on my 65-gallon, and being larger filters, they is a slight motor hum. I have an AC50 on my 20-gallon, and it's totally silent except for the waterfall.

If you get an AC110, yours might be completely quiet, motorwise. One never knows with them. I have found that the lids on mine are warped and don't seat properly unless I work with them for awhile. I find that a pain. That's probably not the case with all of them, however.

As for the function of filtering, Aquaclears can't be beat. They're great filters, overall.

I use the Aquaclears exclusively on my tanks. Aside from the small annoyances mentioned above, I'm very pleased with mine. When I get a third tank, I'll be using an AC on it, too.

-- mermaidwannabe