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DIY Substrate Heating Cables

Recently there have been some posts suggesting that DIY substrate
heating cables are somehow “very risky”.   Having actually build and
used DIY substrate heating cables I feel this isn’t true.  Some
important points about these cables;

Safety  - Anytime you mix electricity and water obviously you have to
be concerned with safety.  However, with the DIY substrate heating
cables there is nothing especially dangerous with them.  In addition
to the low voltage (generally 12V) you have the advantage of the
isolation provided by the transformer.  I’ve seen some concern that
the fine wire used is too fragile and the wire or insulation might
somehow break.  The wire most often used is a #30 wire wrap wire.  The
insulation on this wire can withstand temperatures well above the
boiling point of water and the wire is very ductile being designed to
wrap tightly around small posts without breaking.  There is no way you
are going to accidentally kink and break this wire.  Buried 3-4” deep
in the substrate I don’t see how you could damage this wire.

Difficulty/Effort  - Substrate heating cables are actually one of the
easier DIY projects.  It requires only a basic understanding of
electricity (Ohms law) and is certainly less complicated than wiring
up a fluorescent hood. 

Cost – I put my system in for about $25.  Even for a very large
aquarium you wouldn’t have to spend more than $50. 

Effectiveness – Based on temperature measurements the cables are
certainly effective.  Without the cables on, the bottom of my
substrate runs about 2 deg cooler than the water.  With them on it
will run 2 or 3 deg warmer than the water.  These temperature
differentials will certainly generate micro-currents.  Whether or not
these currents aid in plant growth is another question.

Bottom line – Because of the ease of installation and low cost I
certainly plan to use these cables in any large plant aquarium I setup
in the future.

Jim Spencer
Sayre, PA

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