Will it hurt your tank? No, but neither will sending me 20$.

Hi Tom,

:-) Actually substrate heaters may "hurt" some set ups in hot climates due
to adding more heat. Aquarium coolers are not inexpensive.

Yea, tell me about it:-)

If Adam does decide to install the substrate heater in his tank I would just
give him one advice: make sure you secure it very well to the bottom. Don't
rely on the suction cups alone.

Yes, even the best suction cups, which are made by Dupla are sujected
to movement. Then you do not get the micro currents that Dupla suggest
help.
If currents to the substrate do help, then why not like the RFUG I
used for a about 20 years also not do the same thing? Does the same
thing as the cables, just at a higher flow rate, grows plants
great/the same as cables did over the same time period. I made my own
grill from heat resistent plastic to keep the distance from the tank
bottom the same.

Many folks turn their cables off over the summer months, Folks in SG
don't/cannot use them at all yet routinely set up beautiful tanks.

George Booth runs his AC at 72F so he has a "Dupla" air conditioner
I think he and I beat that horse to death on the APD over the years.
I used reptile heating pads on the bottom of the tanks and I would
certainly argue that these do the same the thing as a cable system.
The increase in bacterial reminerilization of nutrients due to temp
increase could account for slight differences rather than flux.

But substrates and their role in planted aquaria are of great interest
to me on a number of levels.

I've had:

High flow(RFUG's)
Low flow (Cables)
No flow (Just gravels/sand)

over the years to look at the role of flux in/out of the substrate.
No flow, like Claus's discussions with me, produced the best growth of
any of these three systems with root submersed plants.

Regards,
Tom Barr