Underground filters

I have to disagree. With glass bottom tanks, it is very easy to see what is
going on under the UGF. There are no air bubbles. The air stones are located
abotu an inch above the bottom of the lift tubes, so there isn't any way for
air to get under there anyway...
-JD

"atomweaver" wrote in message
...
Tynk wrote in
ps.com:

On Oct 9, 7:20?am, "jd" wrote:
Yeah, I can relate with the cleaning of the crud off th e plates, but
I only do that when I'm tearing atank down, which is hardly ever now.
Since I'm not doing commercial or research work any more, my tanks
are all recreational, and I don't have to tear them down unless there
is a good reason. I have tanks that have been going for 6 years
without a teardown, and they're rock solid.....
-JD


- Show quoted text -

As you and RM mentioned...the crud under the plates is my biggest
*con* when it comes to using them.
(Pay no attention JD to the troll tailing me...we are simply
discussing the pros and cons of them and he has to make it into
something it's not...sorry *for* him).
It's that crud that is basically a ticking time bomb. Often an area of
it becomes a toxic cess pool that can release a toxic gas bubble into
the tank.

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. THe rapidity with which his water
quality dropped (2 days, IIRC) indicates more than just normal metabolic
action of some fish in a heavily planted tank. JD's story may actually be
another indictment of UG filters, as that rapid drop in water quality
might
not have occurred if the UGF wasn't there, but I guess not enough is known
to say for sure.

DaveZ

(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. The rapidity with which
his water quality dropped (2 days, IIRC) indicates more than just
normal metabolic action of some fish in a heavily planted tank. JD's
story may actually be another indictment of UG filters, as that rapid
drop in water quality might
not have occurred if the UGF wasn't there, but I guess not enough is
known to say for sure.


I have to disagree. With glass bottom tanks, it is very easy to see
what is going on under the UGF. There are no air bubbles. The air
stones are located abotu an inch above the bottom of the lift tubes,
so there isn't any way for air to get under there anyway...
-JD


*shrug* Perhaps a UGF dead spot holds the toxics dissolved in water, then.
My own experience with UGFs is limited, and had poor results compared to
modern options.... But, people used UGFs for decades, and they kept FW
tanks just fine. It seems you can make UGFs work for you. Good on ya',
then. HOBs and cannisters are IME much easier, safer and effective, but if
you've got something that works, too, keep at it. 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.

DaveZ

actually, the most probably cause is the fact taht having the UGF lets me
"overload" the system pretty heavily - that is one of hte reaswons I like it
so much. 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. My guess is that the difference in surface area for
bacteria to love on is what really make sthe 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.

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

-




"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. The rapidity with which
his water quality dropped (2 days, IIRC) indicates more than just
normal metabolic action of some fish in a heavily planted tank. JD's
story may actually be another indictment of UG filters, as that rapid
drop in water quality might
not have occurred if the UGF wasn't there, but I guess not enough is
known to say for sure.


I have to disagree. With glass bottom tanks, it is very easy to see
what is going on under the UGF. There are no air bubbles. The air
stones are located abotu an inch above the bottom of the lift tubes,
so there isn't any way for air to get under there anyway...
-JD


*shrug* Perhaps a UGF dead spot holds the toxics dissolved in water,
then.
My own experience with UGFs is limited, and had poor results compared to
modern options.... But, people used UGFs for decades, and they kept FW
tanks just fine. It seems you can make UGFs work for you. Good on ya',
then. HOBs and cannisters are IME much easier, safer and effective, but
if
you've got something that works, too, keep at it. 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.

DaveZ

(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