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alternative heating devices
George wrote:
"Earle Hamilton (used to be (still is?) on this list) built such a system
using
PVC and he had great success with it. He had a long article in AFM some yers
ago
describing the system and how to build it. I think he ran the water through
a
closed PVC pipe system and used a heater and pump to source water at 95 F. I
believe he reported great long term results."
I corresponded with Earle about his article a few years ago and subsequently
built a device similar to his. In my case, I used copper tubing rather than
PVC, covering it with several layers of 2 part epoxy to prevent toxicity
(the epoxy worked - I was never able to measue any increase in Copper in the
tank using a LaMotte test kit and conductivity tests indicated that there
was no area of exposed copper in contact with the water in the tank). I
figured that the copper would be a better conductor of heat than the PVC in
Earle's original design.
I used this device for about 2 years. I was able to measure a definate heat
gradient within the substrate bed and the substrate was warmer than the
water column - check the archives, I'm sure that I posted about this a few
years ago. It DID require a very powerful pump to push even a small flow of
water thru the many twists and turns of the manifold. I think I measured
something like a 90% loss due to friction of the water against the tubing as
it moved thru so many 90 degree turns. So it was expensive to operate.
I never noticed any increase in "stability" due to the heated substrate. I
did notice extreme problems with all KINDS of nuisance algae - but I
attributed that to my overly rich substrate - I think that the heating
manifold might have made things worse by causing excess nutrients contained
in the gravel bed to be carried out into the water column. In the Dupla
scheme of things, the only thing in the substrate is a small quantity of
laterite.
I recently replaced the copper manifold with a 200W AZOO cable and replaced
the gravel to fall in line with standard Dupla methodology. It being summer
and me being without an a/c, the new heating cable hasn't been "on" much yet
so I can't comment on any differences - except that this current setup has
NO nuisance algae. Of course, my definition of nusiance and what others find
objectionable might differ - the front glass does need to be cleaned off
every few weeks. But the plants don't have algae growing on them. (moderate
to low fish load and very light supplemental feeding)
James Purchase
Toronto