al wrote:

ok but do you suck up the surface at all. I guess I am asking if you don't
suck up the fish solid waste - does it naturally break down to safe
byproducts. I have heard of catfish (cory ) loosing barbs becasue of dirty
gravel etc. any thoughts

I try to suck whatever is in the surface out. What I meant was not to go
disturbing the gravel as in penetrating the surface. I have not heard of
catfish losing barbs brcause of dirty gravel. They might get nipped off
by a cichlid though... Nanacara anomala are famous for beating on catfish.

Cheers,

JLD