I've ran and Undergravel filter in my 95 gal
tank since I set it up 7 years ago. I originally did this because thats what we had when I was a kid (in the early 70's). It's only since then that I found many aquarists
don't care for them. I ran it with a powerhead driving each draw tube. I also had 1 Whisper HOB
That setup worked so-so for a few years but I didn't have much success keeping fish I wanted (long story).
After a few mistakes I started hanging out in forums like this and found out a golden rule (at least for FW
): You cannot have to much filtration!
So I replaced my Whisper with 2 Marineland Emperor 400's and using some PVC
pieces, changed the UG to reverse flow. This dramatically improved the water conditions in my tank. This is a planted tank and with the reverse flow, I don't have to worry too much about vacuuming the substrate and disturbing
Just a few months ago I removed one of the Marineland HOB
's and installed a Marineland canister.
Fish, plants are doing well and the water is always crystal clear.
So in general I would say UG filters are a great addition
when used with other filtration devices.