under gravel heating

> From: Paul Rothel <prothel at bright_net>
> Date: Wed, 21 Aug 96 19:40:11 -0700
> I need some advice from the experts.  I am going to redo my 30 gal
> setup and am thinking about going with the under gravel heating
> system(Dupla).  Can someone who has tried it both ways tell me, is it
> really worth it.  If I could gain a noticeable difference I will go
> with it, if its not a noticeable difference I not going to do it.  If
> someone has tried it with heating cables and also without the cables
> did you get a difference?  That's what I am trying to find out.

I have tried it all three (!) ways: no undergravel heating, low
wattage undergravel heating (a la Dennerle) and high wattage
undergravel heating (a la Dupla). 


Plant Growth: These and other setups have shown that proper
fertilizing (including CO2) and lighting are the major factors
controlling plant growth.  We have noticed NO difference in plant
growth with or without heating cables.  We have noticed NO difference
in plant growth with undergravel filters vs canister filters vs
trickle filters (given careful attention to flow rates and CO2 loss).
We have noticed NO difference in plant growth with metal halide vs
fluorescent lighting (given the proper intensity and spectrum).

Algae growth: We have noted major differences in the three UGH setups
concerning algae growth.  

The test case is a 100g heavily planted discus tank.  It was first set
up per Dupla specs but without cables (we couldn't afford them back
then).  It ran great for 18 months; gorgeous plants, excellent water
quality, beautiful fish.  After that time, algae began to be a problem
and plant growth was less robust.  We figure that nutrients in the
substrate weren't being replenished and it just "ran out of steam".  

The tank was then torn down and set up again using Dupla 100w cables
(Duplaflex 300).  This could be considered a "low wattage" setup, much
like that recommended by Dennerle.  Plants grew OK, but algae that was
transferred on the plants remained a problem.  Specifically, fuzzy
green algae (like small cotton balls) continued to plague the E.
tenellus and other fine structured plants.  Also, a dark brown, slimy,
miniature coral-like algae continued to thrive on mechanical
equipment.  Different hair and thread algaes were noted at various
times. Everything but the plants was bleached during the tear-down and
fresh gravel was used so any algae came from the old plants and other
unknown sources (water, air, ???).  The tank was like this for 2 years
before it was changed again.  No improvement was noted.

The tank was recently torn down and set up again using 200w Dupla
cables (Duplaflex 750).  This could be considered a recommended Dupla
setup.  The tank is currently algae free except for small green spot
algae that grows on the acrylic tank itself.  The fuzzy green algae is
gone as is the slimy brown algae.  No hair or thread algae has been
noted after 3 months. Again, everything was bleached except plants. 

A 90 gallon tank has been setup for 4 years with 250w Dupla coils and
parallels the experience with the new 100g/200w tank setup.

A 120g tank has been setup for 2 years with a 100w cable and parallels
the experience with the 100g/100w tank setup. 

Bottom line: Cables won't make the plants grow better but will create
a better and longer lasting environment.  If you think you will only
keep the planted tank setup for a year or so, don't bother with
cables.  If you go with cables, use Dupla wattage recommendations.