I've been a firm believer in UGFs for a long time now. My personal experience has always been great with them... as long as I do frequent water changes and gravel vacs. Recently I was performing a gravel vac and I noticed TONS of waste buildup in the bottom, something I haven't seen in my history of using a
UGF. I thought about why this happened and came to this conclusion: For one part, I was past schedule on the gravel vac, just my stupidity and sorriness, but the biggest reason, I do believe, is the fact that the fish I keep are now getting very large and are horribly messy when they eat. I think a
UGF works fine on a small scale aquarium with small species of fish, but once you keep a larger tank, with much larger fish, they become a problem. The amount of waste these fish produce is very hard to keep up with, no matter what sort of filtration or combination of filtrations.
I still like the thoughts of a
UGF, but do not plan on using another one unless it's on a very small tank. The next tank I build is going to be a sand bottom with some snails to keep it stirred up. Between the snails and my Oscars, I don't foresee a problem.
As for the whole
UGF controversy, I do think it's personal preference and experience. I've posted here before about how much I like them, but after my last cleaning, honestly I was scared. I'm very surprised my fish didn't die! Again, I'd probably run a
UGF on a small scale system, but never on a large tank with a large breed fish.
I really do believe now after much thought, consideration, and research, a sand bed is the way to go no matter what type of tank you have. Whether it is a salt tank or fresh tank, there is much more area for bacteria to thrive and if you have the right critters introduced to the system, there is no reason to worry about your sandbed going bad.
Just my 2 cent...