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In reference to something like this:

[link=http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=11371&Ntt=gravel%20heater&Ntk=All&Ntx=mode+matchallpartial&Np=1&N=0&Nty=1]http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=11371&Ntt=gravel%20heater&Ntk=All&Ntx=mode+matchallpartial&Np=1&N=0&Nty=1" style="COLOR: #C000C0[/link]

Are there any real benefits for planted tanks with this?

I wonder how long these things really function. It's not like you can easily replace it should it die after a year.

Would it help do anything in preventing anaerobic buildup in an Eco-Complete setup? Some areas of my planned tank will not have any rooted plants to keep the soil in motion where oxygenated water can get in. I know gravel vacs can help, or just stirring slightly with a "rake", much like we would in the garden. But I wondered about heat and how it has a tencency to create mild current.

Hi Diane,
Well, like with just about anything in this hobby, there are
those that swear by undergravel heating, and those that
swear at it.

Today there are two systems. One actually heats the tank
water for the fish, by placing the heating element under
the gravel. The other is designed to provide only a slight
amount of heat. Generally speaking they both operate off
of low voltage and high current passing through wire of
known resistance. The resistance converts the voltage and
current into heat.

The theory was (is) that by placing the wires just off the
surface of the tank bottom (the wire actually sits on
standoffs that hold it about a 1/2 inch above the bottom)
the heated water would rise to the gravel surface where
it would dissipate into the tank. As the water rose through
the gravel, it would bring nutrients with it and the would
flow past the plants roots nourishing the plants. Most
commonly this system was used in a layered substrate system.
The wires were laid across the standoffs, sometimes called
"chairs," and then a layer of pure Laterite (clay) was
then placed (molded) around and atop of the wires. Then
a cap layer of regular aquarium gravel was placed on top
of the clay. This kept the clay on the bottom of the tank
where it belonged. With the origional system, marketed
by Dupla, there was just enough heat to cause very very
tiny water currents. The roots were not baked, nor were
they "awash" in water movement. It was just a very gentle
nearly immeasurable water movement. It worked and plants
did thrive. However, many could see no real improvement,
and it was specifically designed to be used with the
Laterite, and gravel system. Dupla still makes and markets
the system (very very expensive) and there are of course
knock offs that are less expensive.

People being people, folks then reasoned that if you could
cause water movement through the gravel by heating it with
the wires, why not simply place a lamp (not good) or some
other heating source under the tank itself, and get the
same results. To that end many tried using the heating
pads that are used for reptile cages (tanks). The thing
is that with these, you wind up heating the tank water too
and while you do reproduce the currents through the water
its not quite the same, and the results were, again, not
quite the same. By the way, if you actually used a lamp,
you wound up with a horrible case of algae on the bottom
of the tank where you could not get to it, and it wound up
creating all sorts of problems.

Now, folks have taken things yet a step further, and created
undergravel heaters that actually replace the tank heater
and are designed to keep the tank water warm. Again, you
get the water movement, this time faster, and it can cause
plant problems, especially if the thermostat system fails
and you cook the roots of the plants.

I know of only a handfull of folks that still use the
undergravel systems. It was a "fad" that was based on
science, and does work, but, as with all fads, its faded
out.

Frank

Additional reading:
http://fins.actwin.com/aquatic-plants/month.200108/msg00570.html

and:
http://aquaticconcepts.thekrib.com/Articles/AFM_Laterite.htm


Last edited by FRANK at 14-Mar-2005 19:11

Last edited by FRANK at 14-Mar-2005 19:16

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Thanks for the history Frank - very interesting read. I knew there was some deep theory behind it and it makes sense, but I can see where issues could arise.

I can't help thinking that such a system could not work for more than a year or two.

I dont see why it would only work for a year.

Literally it is just power going through the wire heating it up. If anything, it should outlast a hang on heater.

- you have more faith than I do .

based on some polls I have run, some people with planted tanks have them ongoing for many years without changing substrate. I have a hard time believing it will run that long, but that's just my opinion of some electronics devices.

Cory_Di
Unless I missed something in Frank's usual excellent answer. There are the heat pads which are placed under the tank. These are used in the Horticulture industry to place under seed raising boxes. They come in various sizes and usually run on a low voltage.

Keith

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My question is why bother with those? If they really help the plants and make them grow faster then I don't want it as I will need to prune my plants even more often. If they don't work, why waste your money.

My advice is to save your money for a nice pressurised system.