sorry I didn't elaborate, but what I've read is that the current created
by
the substrate heaters in concurrance with turbulence created by HOT
filters
negate any postive affect a SH can offer...

is that better? I dont' have any reference for this, just what I've
read
over the last 2.5 years or so....

Are you saying that a HOT filter defeats having a substrate heater, or
that
a HOT filter does the same thing a substrate heater is suposed to?

What I read, was saying that the uplifting currents created by a substrate
heater, has to battle the downstream current put off by a HOT filter... heat
rises, HOT flows down.... the uplifting current is only affective for the
lower 1/3 to 1/4 of the tank, which means, what is pulled out of the gravel,
is put back in the gravel somewhere else...