Re: will not gravel vaccuming kill my fish?

I'm not going to copy any of the previous suggestions,
they're all good.   The major point is,  you cannot ignore
the buildup of anerobic bacteria in the gravel.

UGFs only serve to mask the problem.   The UGF does 
allow aerobic bacteria to use the gravel to remove the
nitrates,  but there will still be pockets of anerobic
bacteria that will only increase as they emit their noxious
wastes into the gravel.

The crud that builds up under the UGF's will slowly 
clog any filtering you had when it was new, and you
 will eventually find that your nitrate levels will creep up 
until you will find your fish having problems that will continue 
to increase.

Bob