Internal filters are not very popular in the US...compared to abroad. That being said I hear good things about the Eheim Aquaball.
Duettos are great for tiny invert tanks and such, Fluvals I have seen work well on turtle tanks and other land/water type tanks, but honestly I don't think that many people are crazy about them for regular tanks.
Have you looked into Swiss Tropicals mattenfilter?
Barring that, I would say use three or four smaller sponge filters (very cheap ones can be had on eBay, Google xy sponge filter) connected to one central powerful air pump, such as a deep water Whisper. You can alternate the maintenance on them, I think that would be a plus. Also maybe use a small Koralia (Koralia nanos, the old style, are going for $15 in lots of places) to up the circulation...
Duettos are great for tiny invert tanks and such, Fluvals I have seen work well on turtle tanks and other land/water type tanks, but honestly I don't think that many people are crazy about them for regular tanks.
Have you looked into Swiss Tropicals mattenfilter?
Barring that, I would say use three or four smaller sponge filters (very cheap ones can be had on eBay, Google xy sponge filter) connected to one central powerful air pump, such as a deep water Whisper. You can alternate the maintenance on them, I think that would be a plus. Also maybe use a small Koralia (Koralia nanos, the old style, are going for $15 in lots of places) to up the circulation...
