Underground filters

(top-posting repaired (again). In Usenet, top-posting = bad manners.
Please keep your elbows off the table, jd. ;-) )
"jd" <hopoe DeleteThis @comcast.net> wrote in
news:ft2dnSVWL7q0CY7anZ2dnUVZ_tijnZ2d@comcast.com:
> "atomweaver" <atomweaver DeleteThis @hotmail.com> wrote in message
> news:Xns99C66AD0B22AFatomweaver@207.115.17.102...
>> (top-posting repaired...)
>>
>> "jd" <hopoe DeleteThis @comcast.net> wrote in
>> news:cJqdnVdwoLJugJPanZ2dnUVZ_vumnZ2d@comcast.com:
>>> "atomweaver" <atomweaver DeleteThis @hotmail.com> 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