Reptile & Amphibian Forums

Sorry for the long question, but I have really been having problems getting my temps right. I have a 40 gal tank (for a ball python) that I'm trying to heat to 93 on the hot side, low 80's everywhere else.

My tank stand is a wooden frame with insulating foam in the center area - The tank sits on the frame, and there is about 1/4 inch between the tank's glass bottom and the insulating foam.

I first tried attaching the flexwatt to the glass itself, but with my on/off thermostat it was getting too hot. Also, no heat was getting to the 'cool' side. So what I was thinking of doing is using two rheostats with 2 pieces of flexwatt (11 inch) in conjunction with the on/off thermostat so that one piece is 93 when on, and one piece is 82 when on. Then the thermostat will basically just shut off if the temp gets too hot or there is a flexwatt failure.

Is this the best idea, with the flexwatt touching the glass, or would it be better to try to heat the whole 1/4" area underneath the glass by putting the flexwatt on top of the foam (essentially 1/4" away from the glass) and running it at a higher temp?

I read your post very quickly on my way out. Sorry if I missed some of the points of your question.

I believe you have some more simple things you can experiment with.

Get a scrap piece of 1/4" Sintra from a sign shop and sandwich it between the flexwatt and the bottom of the tank. The Sintra should touch both the flexwatt and the bottom of the tank.

Increase thermal mass over the heated area. Clay hides, rocks, things like that.

If the tank has a screen top, cover much of it with foil. I may also suggest covering the insulation with foil but I'll need more information first. More on that later...
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Current snakes:

0.1 Gonyosoma oxycephala - (Silver/Yellow)

1.2 Gonyosoma oxycephala - (Green)

7.6 Gonyosoma janseni - (Black)

0.1 Gonyosoma janseni - (Black & Tan)

So basically, the flexwatt does not have enough mass and heat retention capability to heat the area underneath the tank. Therefore, if I get this Sintra stuff, The flexwatt will heat it up and that is what will be heating the tank. Is this correct?

Also, I do have the top covered, it just has some small vent holes.

>>So basically, the flexwatt does not have enough mass and heat retention capability to heat the area underneath the tank. Therefore, if I get this Sintra stuff, The flexwatt will heat it up and that is what will be heating the tank. Is this correct?

Without knowing exactly what your conditions are, that is my best guess. Sounds like you have a pretty good idea of what I'm talking about.

With heat tape, in order to raise ambient air temperatures on the cool end, the hot side may have to be uncomfortably or even dangerously hot for the animal. Conversely, the proper temps on the hot spot may not be enough to heat other areas of the cage.

This is especially amplified in large cages in relatively cool rooms.

One way to deal with this is to increase thermal mass directly around the hot spot.

In fact, before you call and drive all over looking for a scrap piece of Sintra, maybe just try increasing the thermal mass inside of the cage. You could probably just go back to having the heat tape contact the underside of the tank, in fact. Use some rocks, clay posts, or even an empty ceramic water bowl.

For reasons I won't explain right now, I still like the idea of Sintra between heat tape and glass. If the thermal mass inside of the cage works I would then start looking for Sintra. I can explain why if you like.

Lastly, what type of insulation do you have underneath the tank? Is it foil-faced? I may have a suggestion that will make your setup even more efficient, although I don't think it will matter.
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Current snakes:

0.1 Gonyosoma oxycephala - (Silver/Yellow)

1.2 Gonyosoma oxycephala - (Green)

7.6 Gonyosoma janseni - (Black)

0.1 Gonyosoma janseni - (Black & Tan)

The insulation I have is this piece of 1.5" styrofoam insulation that I got from home depot. The tank essentially sits on top of this, but the glass of the terrarium is about 1/4" off the 'ground', creating a 1/4" area between the styrofoam insulation and the terrarium bottom.

On a side note, I got another piece of flexwatt today that I will be wiring to a dimmer. So I will have 2 pieces of flexwatt to work with now - one with a dimmer and one without.

>>The tank essentially sits on top of this, but the glass of the terrarium is about 1/4" off the 'ground', creating a 1/4" area between the styrofoam insulation and the terrarium bottom.

If you have it, maybe put a layer of aluminum foil down on the styrofoam. I feel obligated to mention that styrofoam is not a fire-rated product so a flexwatt malfunction could be bad. Don't get me wrong, many of us have done it, but I feel I should mention it whenever suggesting changes.

Go ahead and wire your new flexwatt. But I still suggest increaseing the thermal mass inside of the cage. Experiment and see what temperatures throughout the cage are like.

Once you're happy with your setup I do suggest a piece of Sintra between the heat tape and glass.
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Current snakes:

0.1 Gonyosoma oxycephala - (Silver/Yellow)

1.2 Gonyosoma oxycephala - (Green)

7.6 Gonyosoma janseni - (Black)

0.1 Gonyosoma janseni - (Black & Tan)