I have an Ultima II 2000 on my large tank. I also have a sump under the tank for redundancy, but I think It could run on just the Ultima alone. I've found that if the pump is pushing to much water through the filter, it pushes waste back into the display tank. I think that's what
pacu mom
is referring to. I have a ball valve on the outlet side of the filter that I close slightly to slow down the flow and it keeps waste from re-entering the display tank.
I currently run my filter on a Reeflo Dart/Snapper, and it pushes to much water through the filter (that's why I have the ball valve on the outlet). I recently purchased a used Red Dragon 3 (DC 100w version) to hopefully cut down on energy cost and noise. The Red Dragon should push approximately the same GPH of water, so hopefully it works.
I bought my Ultima and Reeflo pumps used about 3 years ago. Not sure how old they were already, but I'd say they're probably 10 years old now. As others have stated, the backwash feature is priceless for doing water changes. I have a 50' soft hose that I roll out either into the yard or the nearest bathtub that I connect to the filter when I need to clean it out. Takes about 10 minutes to drain 200ish gallons of water.
My only complaint with the Ultima is that it doesn't always seal correctly when I change it from backflow to filter to rinse. This could be because it's old/well used and it could be because my inlet hole in the aquarium is about 8" off the bottom of the tank, so it sucks in some sand every once and a while. So I think there's sand trapped in the filter gasket, not allowing it to seal completely sometimes.
I just purchased a gasket replacement and new media for the filter. I plan to replace that in the next couple months and I'll put updates on my thread for that process. The reason why I'm changing filter media is because I don't even know what's in there right now. I bought it used and I could feel/hear media in the filter when I was hauling it around but was to nervous to open it up, thinking I'd screw something up at the time.