The Fluval C Series HOB filter line is just too small for a 75 gallon IMO. I wouldn't even think about using them on a 55 gallon. I mean you could do it, but I wouldn't. I like aquaclears, but in some instances where space is limited (trouble with maintenance) and in spots I could never risk flooding I stick to penguins. The filtermax III prefilters will make flooding much less likely to happen. I use the prefilters on my aquaclears and don't have to clean the media in the HOB very much (the prefilter catches ALOT of the waste). Every other waterchange, I squeeze out the prefilter thoroughly. Personally my aquaclears have never flooded, but a couple of my friends have told me of expeirences where the sponge floated up and drained water on their carpet/floor. I stick as many HOB's that will fit on each tank. For a 75 gal with only HOB's, I think I would use two aquaclear 110's provided space reqirements for maintenance allowed in my stand area.
The penguins (350/200) have similar baskets too, you just gotta buy em seperately.
