There's crud and there's crud. A certain amount of detritus (mulm) is
acceptable, even desirable, especially in a planted tank. But if you don't
want tons of uneaten fish food rotting in the gravel. And most people vacuum
the gravel of unplanted tanks, to keep the substrate from going bad.

You don't have to do this with a planted tank. The plants will keep the
substrate from going bad, by absorbing the mulm and bringing oxygen into the
gravel.

A lot of people keep goldfish in bare-bottom tanks. Goldfish are really pond
fish. They are big, do best in schools, and produce a lot of waste. Often,
people are only keeping them indoors for the winter. Water quality can be a
real problem in an aquarium, and it's hard to keep plants with goldfish: they
eat them.

So I guess my answer is that it probably is good for goldfish, but that doesn't
mean it's good for every tank.


Leigh

http://www.fortunecity.com/lavender/halloween/881/