Re: Decorations with UGH

Hi Everyone,

Winter drags on, some days it seems like this list is the only bright

David Cooke was wondering about heat buildup under rocks when using UGH and
asked what measures people have taken to prevent any possibility of the
heat causing the glass bottom of the tank to crack. The engineeres around
here can give their (much valued) answers, but here's what I did:

My 120g tank sits on a welded metal stand (2" square box steel) with a 3/4"
thick hardwood plywood top finished to within an inch of it's life with
about 10 coats of polyurathane (a lot of work but the exposed parts have
the same gloss and depth that a rubbed "piano finish" has). On top of this,
I placed a 1" thick sheet of rigid foam insulation, bought for a few
dollars at a local building supply store. When the tank was positioned
where I wanted it on the top of the stand, I cut the insulation it was
sitting on, leaving a 1" lip of foam insulation exposed all around the tank
(I'll cut some wooden molding to cover it someday).

Before I placed the gravel into the tank, I filled it with water to test
for leaks (120 gallons of water all over my hardwood floor is NOT something
I'm looking forward to). I noticed that due to the great weight of the
filled tank, it sunk INTO the foam about 1/4". As the tank has a plastic
"frame" on the bottom along the edge, there was a considerable space
between the vast expanse of glass in the base and the sheet of foam. I
emptied the tank of water and obtained several 1/4" sheets of the same
rigid foam which I cut to fit under the tank, inside of the plastic frame,
filling up the space. I figured that if the tank + water sunk into the 1"
sheet of foam by about 1/4", then the tank + water + 300 lbs of gravel
might go even deeper (I know, not very scientific, but as one VERY
respected person around here recently pointed out to an overly eager
college student with too much time on his hands - not ALL successeful
aquarists are scientists.)

O.K., so the empty tank is siting on a solid welded metal stand which is
covered by 3/4" of plywood. Level, VERY level. The rigid foam insulation
underneath the tank supports the tank frame AND the glass base of the tank
evenly. I suppose it also provides some insulation for heat loss through
the bottom of the tank as well, but that was a minor secondary
consideration initially - I was more concerned that the glass base NOT be
under any uneven stress which migh cause it to crack, or to cause the
silicone seams to fail.

I was now ready to put in the undergravel heater and the 300 lbs of gravel.
I took one look at 6 - 50 lb bags of gravel and figured that I wanted some
cushioning between it and the bottom pane of the tank, so I went to a local
craft store and bought a number of sheets of "plastic needlepoint canvas".
It comes in sheets about 12" X 18" and is full of holes. I placed an even
layer of this material on the glass base of the tank, and then put the UGH
manifold in place. I read all of the files about DIY heating cables and was
scared half out of my wits, so my design is based on an article which
appeared in AFM a few years ago. The author of the article was good enough
to give me plenty of advice and I made the manifold out of 1/2" copper pipe
(the same kind that is used in residential plumbing). I'm no better at
soldering than I would be at electrical work so I used "Copper Bond" epoxy
to hold the joints together. I didn't want the heating manifold laying
directly on the bottom of the tank for two reasons - one was the
possibility of heat buildup on the bottom glass (call me paranoid!) and the
other was that I figured that if it was raised off the bottom slightly
there might be more of a convective flow of water set up due to the heat.
In order to provide this offset, I epoxied short lengths of copper pipe
(closed at both ends) to the bottom of the manifold. The entire manifold
was given three good coats of marine grade epoxy and then tested for both
leaks and bare copper exposure (it passed both tests easily).

Once the heater manifold was in place, I put in the lower layer of my
substrate, which consisted of a mixture of peat granules (Sera brand), Red
Art Clay, Terralit, Dupla Duplarit and gravel. This layer is 1" thick, the
top of it being flush with the top of the heater manifold. As I was
intending to use several very large (and very heavy) granite rocks in the
tank (same material that the gravel is made from), I was concerned that the
weight might damage the heater manifold and could scratch the epoxy,
exposing the bare copper. To protect the heater manifold, and once again to
distribute the weight evenly, I covered the heater manifold / enriched
gravel layer with a layer of plastic eggcrate. I filled in the grid spaces
of the eggcrate with clean gravel and then placed the large rocks directly
on top. Finally, the rest of the gravel was washed and put in place, giving
me a clean gravel layer that varies between 3" - 5".

Now, this tank has only been set up and running since just before Christmas
of last year, so it's still pretty new. But its working well so far. I
can't even SEE the large rocks which I placed in the tank (the plants are
growing VERY well) and it hasn't sprung any leaks. I have a high precision
mercury thermometer (reads to 0.2 C) and by sticking it into the gravel
around the tank I can measure very definate convective zones of temperature
difference, depending upon whether the thermometer is over one of the
manifold tubes or not. The eggcrate material MAY cause problems later on if
plant roots get wrapped around it but I'll be willing to loose a few roots
if I have to move a few plants to gain the absolute stability the eggcrate
gives my lowest layer of substrate. The substrate heater is providing ALL
of the heat for the tank (save for that added by the suspended metal halide
lights) - the tank temperature ranges from 78.5 F in the morning to 80 F in
the evening, with the gravel being usually 3 - 4 degrees warmer. Time will
tell how it all works out, but I'm satisfied so far.

James Purchase
jpp at inforamp_net