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BioPlast Substrate Heater

*** Note: Steve P., I don't wish to raise your blood pressure any higher
than it already is, so please skip this message about substrate heating...

A short while back, someone asked about the BioPlast substrate heating
system. A search thru the archives gives several hits but nothing definitive
about the BioPlast. George Booth said at one point that he doubted any such
system could give off enough heat to be of any use.

Anyway, I bought one and have it sitting in front of me right now. Mmmmm,
certainly a simple little device, and I can see that it would be very easy
to duplicate it as a DIY project, should it prove to be of any use

The BioPlast consists of a six inch long heat exchange coil made of a rigid
black plastic. Short lengths of flexible black hose are attached to the top
and bottom of the coil, allowing the substrate cable to be attached at the
bottom and the input cable attached at the top. Also included is a "Y"
connector designed to be placed in-line with the water return of an outside
canister filter, with the water for the BioPlast being split off from this
source. Water flows from the filter output hose, thru the "Y" connector and
proceeds thru the heat exchange coil, which would be placed around a
submersible aquarium heater. The water is supposed to pick up heat during
this trip (I guess that if the flow rate is very high, not much heat
exchange would take place). From here, the water flows through a 10 foot
long flexible black plastic hose which is meant to be placed under the
substrate. The water exits from the far end of this tubing and there is a
suction cut provided for this end to be attached to the side of the tank
near the surface. An optional extension kit is available which is just a
connector and another 10 feet of flexible black plastic tubing. Mention is
made in the instruction sheet (very clearly written) of installation rails,
supposedly included, which are used to hold the tubing to the bottom of the
tank. My kit did not contain anything like this, but as I usually use a
sheet of plastic embroidery screning on the bottom of a tank to protect the
glass, I guess that I could attach the cable to this with monofilament.

Not very elaborate, not very complicated. A simple flow through system,
using the output of a canister filter (or alternatively I suppose a power
head), a simple coil heat exchanger wrapped around a submersible heater (not
part of the kit by the way, you supply your own heater), and a lenght of
tubing to get that warmed water underneath the gravel where it is supposed
to create convection currents.

As we have all recently seen, even the subject of substrate heating can
cause some people to get excited (perhaps we could wrap these things around
a few list members - they seem capable of generating quite a bit of

I cannot, at this point in time, say if this thing works - but it should be
a simple matter to see if it is capable of producing a heat gradient within
a substrate. I have a spare tank and a really accurate mercury thermometer
(designed for darkroom use), so I should be able to say in a short period of
time if the BioPlast is able to provide warm/cool zones within a substrate.

I remember last year, when I built a heating manifold for my large show tank
out of epoxy coated copper tubing and pumped heated water thru it, that I
was able to measure a heat gradient of 4 degrees C within the substrate of
that tank. But whether that was enough of a difference to promote plant
growth is questionable, as I did not have a control to compare it with. That
system is currently no longer operational and I am planning on removing it
from the tank within the next few months when I re-set the tank.

George, or any other list member who has substrate heating coils, what is
the heat gradient measurable within your substrate (over a coil vs. not over
a coil)? Is there any literature or experience (or even agreement) over how
much of a heat gradient is required for these things to work (given the fact
that we can't even agree on the mechanism by which they DO work)?

Stay tuned....

James Purchase
Toronto, Ontario