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Alternatives to Cable Heating


  1. Hot Gravel & Laterite source
    by Earle Hamilton <> (Tue, 15 Aug 1995)
  2. UGF/heater method
    by (Karen A Randall) (Thu, 14 Mar 1996)
  3. Heating Cables
    by Neil Frank <nfrank/> (Sat, 26 Sep 1998)
  4. BioPlast Substrate Heater
    by "James Purchase" <jpurch/> (Mon, 4 Jan 1999)
  5. BioPlast Substrate Heater
    by "Phil Barber" <phil/> (Fri, 8 Jan 1999)
  6. Poor Mans Substrate Heating
    by "Richard J. Sexton" <richard/> (Thu, 7 Jan 1999)
  7. UG heating
    by krandall/ (Wed, 06 Jan 1999)
  8. ug/heater
    by krandall/ (Tue, 13 Jul 1999)
  9. Cables
    by Thomas Barr <tcbiii/> (Mon, 01 Jan 2001)

Hot Gravel & Laterite source

by Earle Hamilton <>
Date: Tue, 15 Aug 1995

Tried responding directly to Nick Livingston re substrate heating but 
message didn't take so I will try through the general mailing.  Sorry if 
this is boring to others of you.
Nick, Phil Smelt and I wrote the hot gravel article telling how to build 
a pvc heater cheap and good.  Yes, it really does work.  I would suggest 
you keep the heater size to about 1 watt per gallon and set another 
heater/thermostat in the tank at a lower lever for the cooler wx 
requirements.  While the ugh works, there is still some question in my 
mind as to how necessary it is.  I am doing an experiment where 1/2 of a 
230 gallon tank has ugh with laterite and the other half has ugfilters.  
So far there is no strong indication of difference between the halves of 
the tank with both sides doing great.  I think this is because I found an 
almost free source of laterite.  If you read TOA you will note they 
recommend using 1/3 laterite mixed into the gravel and use that mix for 
the bottom 1/3 of the tank.  This is in conflict with the Duplairit 
instructions which would have you use much less.  Since Duplairit costs 
about $50 per pound and since I had free laterite, I used about 35 pounds 
of laterite for the 1/2 side of the 230 gal tank.  I suspect the 
translation from Ger to Eng in TOA was a bit muffed because with that 
much laterite in the tank some dispersed across the plexiglass barrier 
and into the ugf side.  Thus there was considereable suspended laterite 
throughout the tank.  It took several weeks to clear but eventually the 
tank was fine.  So I don't know if my approximately equal growth on both 
side is becuase of lots of laterite or in spite of lots.

UGF/heater method

by (Karen A Randall)
Date: Thu, 14 Mar 1996

Although I am not the person who developed this method, (it was 
developed by Claus Christensen of Tropica in Denmark) I am the 
person who introduced it both to AGA and APD members.  

The advantages are that it is simple and inexpensive to install, 
and the electrical parts are easily accessible in the event of a 
failure.  Best of all it works. I have been running the system for 
almost 2 years now, as have several of my friends.  _ALL_ of us 
have seen increased growth and vigor in our root feeding plants.

The only possible disadvantages would be the fact that it probably 
doesn't move water evenly through the substrate, (but there are 
many people who don't think cables do either<g>) and the fact that 
it keeps the substrate the same temperature as the tank water, not 
warmer.  It _definitely moves enough water through the substrate 
to keep the bottom of the tank as warm as the rest of it.

Place a UGF plate in the bottom of the tank.  If you are using a 
fine substrate that might fall through the plate, wrap it in 
fiberglass screening first. (I use monofilament fishing line to 
"sew" the screen around mine) Put the riser tubes in place, and 
put your substrate on top of the plates.  Now comes the biggest 
difference between this system and a standard UGF.  Instead of 
placing airstones or power heads in the risers, drop a 7.5W 
submersible non-thermostatic down each one. (I use 2 in a 55G 

The warm water rising in the tubes moves water _very_ slowly 
through the substrate.  Remember that the purpose is to warm the 
substrate and bring nutrients down into it.  it can _not_ be 
expected to serve the function of an under gravel _filter_ when 
run in this manner.

Some people have mentioned experiments with plenums in planted 
tanks similar to those now being used by many reef keeper.  I 
wonder if part of the success of this method is the slightly 
anaerobic "empty" space under the substrate.

Heating Cables

by Neil Frank <nfrank/>
Date: Sat, 26 Sep 1998

At 03:48 PM 9/25/98 -0400, you wrote:
>From: Jim Spencer <>

>The primary reason I use heating cables is to prevent the substrate
>from getting cold.  The room my aquariums are in can get quite cold in
>the winter and without the cables the substrate will run several
>degrees colder than the water.
>Finally, because DIY cables are inexpensive, simple to install and are
>generally a set and forget it accessory I would put them in any large
>aquarium I setup.

Two important comments:(1) There is another way to keep the substrate from
getting too cold and (2) I successfully grow plants and I have NEVER used
heating coils.

The alternative way to keep substrate from getting too cold is to place a
sheet of insulation board under the aquarium. It can be styrofoam or
thermax foam board. The R value is 4 -6 and cuts down the heat loss
tremedously. The tank doesn'f have to sit on the board. It can be wedged
thru the stand to cover the bottom glass (if the stand is open). I have
been doing this for almost 20 years... even before I kept so many plant
tanks. I did it to save on the electricity cost of heating tanks (when
using individual tank heaters). I once published the $$ savings... I think
in 1983.... you can save bucks.  The only tanks that do not use an
insulation board are ones on multi-tank stands where one tank is sitting
directly over the heat generating lights of the tank below. These may or
may not produce convective currents, but I don't care (see 2nd paragraph
below). I still keep a foam board behind the back glass to conserve heat.
Most of my tanks are in one small room, so even in the winter the room
stays warm. If they were in an cold basement, I might use the foam bd on
those plant tanks too.

One reason I never used heating coils is that the room holding my tanks
gets too hot during the summer. I don't want to install an air conditioner
just to maintain the convective water current of heating coils. Some people
put the coils on a timeer and only run them for one hour per day.  I
already generate too much heat from all the damn lights <g>.. so I donit
want ANY extra  heat from the cables. In theory, heating coils are a great
idea. First, I think that heating coils can't hurt. Second, they will be
especially helpful during the initial tank start up  (before the plants are
creating a desireable substrate environment) and during temporary periods
when plants may be doing poorly in an established tank. But when enough
healthy plants fill the substrate, the plants transpiration system will
move water thru the soil (from roots thru leaves)... and their aerenchyma
provide O2 to the roots to create a healthy aerobic micro-zone in the
vicinity of the plant. Together, these mechanisms accomplish the same
objectives as the heating coils! Someday, I will have tanks in a colder
space that will enable me to see if I can get more stability and even
better growth with the use of heating coils... as suggested by a few other
experts that contribute to this list. Maybe it will help with some specific
plants or some combination of plants. Until then, I continue to say that
"Heating coils are nice, but not necessary. They may generate unwanted,
undesireable heat during the summer, and if they are turned off during the
summer, their advantages of creating long term stability are lost.  They
are the LAST thing that a newby wants to add to a plant tank."

Neil Frank

BioPlast Substrate Heater

by "James Purchase" <jpurch/>
Date: Mon, 4 Jan 1999

*** 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

BioPlast Substrate Heater

by "Phil Barber" <phil/>
Date: Fri, 8 Jan 1999

I've seen and read a little about the Bioplast system of substrate heating
and wondered if it delivered the goods; ie:- temperature gradients in the
substrate.  I set up a 30lt tank with a DIY heating tube and thermocouples
linked to a datalogger to try and establish a temperature profile.  It did
pickup heat from the 25W heater, I could detect heating pulses of about
1.0'C in the exit water.  I couldn't detect these pulses on the outer skin
of my buried tube (plastic electrical earth sheath) and couldn't be sure
within the errors of the system  that it generated the desired temperature
gradients.  In the longer term it needs a fair amount of attention to keep
it running.  Small bubbles and particulates get drawn into it and eventually
stop the flow.

I don't mean to say that the concept doesn't work only that you should
verify the operational aspects, be prepared to tweak it and maintain it.

Phil in an unusually warm Croydon (.... erm ... that's south London)

Gee I'd better get back to lurk mode and safety!

Poor Mans Substrate Heating

by "Richard J. Sexton" <richard/>
Date: Thu, 7 Jan 1999

I've done this and got pretty good results. You'd think
I'd meeasure the temperatures, but, oh no, that would have
been to easy.

Silicone cement a fluorescent ballast to the underside of a 
tank; use it to drive the tanks in the shelf below. This
obvioulsy only makes sesne where you have a rack of tanks.

- --
Richard J. Sexton                               
Maitland House, Bannockburn, Ontario, Canada, K0K 1Y0       +1 (613) 473 1719

UG heating

by krandall/
Date: Wed, 06 Jan 1999

>While reading the current post about substrate heating I thought of
>something that would possibly be good to try.  Take a standard
>ungergravel filter and put a heater in the stack (may have to oversize
>the stack some) then connect the top to a powerhead and reverse the
>flow.  Seems to me that this would a) reverse the flow of water in the
>standard rugf systems, b) heat the substrate first and heat would 'rise'
>to the top c) keep the organic crap in the substrate to a minimum.  The
>drawbacks that I see are a) the heater may cause damage to the stack
>(like melting) the water aggitation may reduce the heat causing the need
>for a larger heater to be used.

This is a variation on an already tried and true, inexpensive set up.  You
don't really need powerheads or oversized uplift tubes.  The small 7.5W
non-thermostatic heaters fit in normal size uplift tubes without any
problem at all.  They create a very slow current in the uplifts (like heat
going up the fireplace chimney) which moves water slowly through the
substrate.  This _does_ work... I've measured the temperature difference in
the substrate between tanks with and without this system in the same room.
It obviously doesn't heat the substrate to a temperature HIGHER than the
rest of the tank, but does solve the problem of "cold feet" in a cold room,
which I truly believe is the biggest advantage to substrate heating.  

There are other simple methods that also help alleviated the stratification
of cold water in the substrate.  But this one does work well.
Karen Randall
Aquatic Gardeners Association


by krandall/
Date: Tue, 13 Jul 1999

Adam Weingarten  wrote:

>I'm about to set up a new 72 gallon tank and I was considering if it would
>make sense to heat the substrate in some way.  I don't like the idea of
>substrate heating cables because having live wires in my tank just doesn't
>seem like the safest thing in the world. Ihave read up on the udea of using
>a ugf with a heater in the uplift tubes to destibute the heat. I was
>confused about this alternative because I failed to see why the heat goes
>down into the subtrate instead of merely going out up the tube. 

The heat from the heater DOES go up the tube... in the form of warm water.
As the warm water rises, it is replaced from water from below, which in
turn draws water from the water column into the substrate.  It works just
like a chimney on a fire place.  If you don't have an updraft of warm air,
your house will fill with smoke.

This method does NOT warm the substrate beyond the general temperature of
the tank.  It just pervents stratification of COLD water in the
substrate... something that's very likely to happen in a tropical aquarium
in a cool room.



by Thomas Barr <tcbiii/>
Date: Mon, 01 Jan 2001

John Caddy wrote: 
> Arizona Aquatics carries a different kind of substrate heating system
> that appears plausible. It uses a powerhead to push conventionally
> warmed tank water through tubing that runs under the substrate. See
> their substrate page. Does anyone have experience with it?

I did this many moons ago with PVC tubing under the gravel. IMO, the warm
water method doesn't get warm enough to cause enough flow to happen.
As the water passes through the line it loses heat as well. I used big 1/2
PVC and CPVC to do this and if you use smaller tubing or lower flows this
will be even more of a problem, especially on a big tank/long lines.
Cables/pads don't have this issue to contend with. Heating is much more
even. That's a big one for this method.
The cables that I bought(dupla/sandpoint), used(other folk's), built(DIY)
did do better. Cables are hard to say whether they help or not but I felt
the warm water approach did not cut the mustard for the idea to work well.
The cables did better IMO.
The reptile heater mats are good as well and dirt cheap if you got to have
cables or heat etc. Just stick em on the bottom of your tank get a temp
controller for 15-25$ or so and your done.

If you want to test the usefulness of cables/pads etc just turn them off and
see what happens.

I do not use cables or heated substrates anymore on my own tanks but still
maintain one that does.
FWIW, I have removed a dupla set up on one tank and replaced it with 100%
flourite. The owner is quite happy and has been for about 18 months now.
Flourite does not need to be plugged in:) Set and forget.

If you got have some heat, do the retile pad or a DIY cable set up. That's
the best bang for the buck. The commercial units are pricey. I did a nice
DIY'er for about 20$(no controller but they can be had cheap as well). If
you can find the cable size you need....that's the big issue. Reptile pads
are dirt cheap as well. I have not seen or heard a good enough argument to
say a cable versus a pad will do better somehow than another. Personally
having tried both over some time, I can't say there's a difference either.
The warm water approach is the most doubtful and often requires a more
complex system for your tank than say a reptile pad which is outside your
tank. Hydroponic places sell warming mats that can go inside your tank as

The ambient temperature is the big issue for using cables or other forms of
heat. If you set the temp to be 80F what happens when the summer temp is
averaging 85F? They shut off. If you want to use them I would suggest having
a maintained temp in your house. That's what George does:)
Tom Barr

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