(top-posting repaired (again). In Usenet, top-posting = bad manners.
Please keep your elbows off the table, jd. ;-) )
"jd" wrote in
:
"atomweaver" wrote in message
...
(top-posting repaired...)

"jd" wrote in
:
"atomweaver" wrote in message
I'm not big on fluid dynamics, but it seems totally plausible to me
that JD
was holding such a bubble in a static location (a "dead" corner?)
under the
UGF with the flow from his air pump, and the failure of the pump is
what allowed it to diffuse into the tank.
I have to disagree. With glass bottom tanks, it is very easy to see
what is going on under the UGF.
Still, a big water
swing
in two days with an active operating cannister filter is an
indication that
something more was going on in your tank. Big die-off in the UGF
bacterial
colony itself, maybe? Once you stop flowing water in the UGF, that
underplate area could go anaerobic pretty quickly, kill off your
bacteria colony, and then diffuse into the tank from there.
(another) *shrug*... like I said, not enough known to say for sure.

actually, the most probably cause is the fact that having the UGF lets
me "overload" the system pretty heavily - that is one of the reasons
I like it so much.

Understood. You can crowd the tank, since you've got more surface area
of gravel with active bacteria.

What was really interesting was that when the
canister tanked, the water quality didn't really change, but when the
UGF tanked, there was a pretty fast crash.

WHy is that interesting?

My guess is that the
difference in surface area for bacteria to love on is what really makes
the diff - the canister has a lot less surface area for bacterial
colonies than the huge gravel bed (a 125 tank, 2-4 inches of gravel,
as opposed to a (roughly) 1.5 gallon canister.


Right. So when you do go down, you've got more biomass in bacteria dying
off, _and_ more fishies making number 2. Which is the greater factor in
water degradation? Dunno, myself...

I agree that UGFs aren't for evreyone, but (like almost any tool that
can work) eliminating them out of hand is foolish. If you've tried
them, and not had luck, they obviously aren't for you. My main point
was that they have a bad rep that, in my decades of experience, is
undeserved.

Bad rep? No. They have advantages and disadvantages, and for many in
the hobby, those trade-offs don't line up with their preferences. Given
what you've said about over-stocking a tank, I'd guess it has to do in
part with system stability when the power goes off.

When I work with newbies to set up tanks, I always start
them out with a UGF as a component of their filtration system.

I hope you tell them about how easy it is to over-stock the tank... If
they (like me) have blackouts from time to time, its an advantage to have
tanks which can sustain themselves for a while, or at least know that
once the power goes off, you've got a situation on your hands.

If they
decide they don't like it, they can always simply pull out the lift
tubes. The space under the plates will fill pretty quickly with loose
gravel (no caps on the lift tube holes), and the only real difference
is that there is a bit of extra plastic inthe tank...

Don't you use some sort of a screen mesh to keep the gravel above the
plenum?

DZ
AW