# under tank heater placement



## Mountainfrogs (Jan 23, 2012)

I received my under tank heater today. It is 10" by 17". I think it may be a bit big but hopefully ok. Should i mount it under the terrarium, on the side, or on the back. I will have 2.5 inches of water and 3-4 inches of substrate. The background and sides are made with gs foam and cork bark. I also will be connecting a dimmer to the heater to regulate the tempurature. Here is a picture of the tank with the background done except for the coir on the foam. Thanks in advance for any input.


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## james67 (Jun 28, 2008)

Mountainfrogs said:


> I received my under tank heater today. It is 10" by 17". I think it may be a bit big but hopefully ok. Should i mount it under the terrarium, on the side, or on the back. I will have 2.5 inches of water and 3-4 inches of substrate. The background and sides are made with gs foam and cork bark. I also will be connecting a dimmer to the heater to regulate the tempurature. Here is a picture of the tank with the background done except for the coir on the foam. Thanks in advance for any input.


NEVER mount a UTH to a tank holding water or which may come in contact with water. its a great way to shatter the glass and destroy the tank. this is also dangerous to the animals for the obvious reasons (broken tank = injured, deceased, or escaped animals)

i dont mean to sound harsh, but all UTHs have this warning printed on the box, the product or both. 

your best bet is to use a submersible aquarium heater (kept submerged in the false bottom). most come with internal thermostats and newer models have a fail-safe shutoff to avoid cooking inhabitants if the thermostat breaks.

james


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## Mountainfrogs (Jan 23, 2012)

I appreciate your input, and after reading your post I decided to consult the owner's manual for the under tank heater which is an exoterra heat wave rainforest. Nowhere on the box nor in the owner's manual was I warned to not use in conjunction with water, on the contrary water is listed as a suitable substrate. It is my understanding that you are correct that it can cause cracks, but not just because there is water in the tank, but because of temperature fluctuations. ExoTerra states "Make sure to use warm (30ºC)
water when adding it to the tank to prevent cracks in the bottom glass,
as it reacts to temperature changes." Before I attach the heater to the tank I will call ExoTerra to make sure I can use this heater with my vivarium. Does anyone else have any pros/cons to the under tank heater attachment and location?


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## Johno2090 (Aug 31, 2011)

I had this same response when I first came here. Glass is very thermally stable and is not very likely to crack unless you have extreme temperature fluctuations. I've used an under tank heater for 4 months now with no issues, you'd have to be daft to pour cold water in the tank and shatter it. 

Use caution and don't cut corners but it's simple and safe in my experience.


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## Johno2090 (Aug 31, 2011)

Oh and it's placed in the centre of the tank on mine and spans the whole length. I do find I need an extra mat on the side pain of glass when the temperature in the room drops too much. I think the substrate may be too thick in my tank.


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## Mountainfrogs (Jan 23, 2012)

how deep is your substrate? with water and soil I am looking at around 6". Thanks for the positive response, I appreciate it.


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## Johno2090 (Aug 31, 2011)

I'll measure it out and let you know when I get home. The substrate and water is always warm though from the bottom, it sits at about 25c at the soil surface.


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## james67 (Jun 28, 2008)

its not just about pouring cool water on the glass. 

for instance: the power goes out long enough for the water in the false bottom to cool to lets say 50-60, then the power comes on and your pad heats very quickly , the glass, to well over 100. 

its just not a great idea. aquarium heaters have been used for years in this hobby with success, im simply suggesting you consider sticking with a known safe long term option.

james


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## Johno2090 (Aug 31, 2011)

James, Have you ever used one yourself? Aquarium heaters heat up much faster so would be more liable to shattering.

The Under-tank heaters are Low wattage they don't suddenly heat up to well over 100 (not sure 100 what thought?) mine UTH is 48 watts. Even if they did the water on top would cool that glass and exchange the heat until it was all equal temperature. As I've said glass is a thermally stable material and is hard to shatter through temperature change. Look at how many idiots pour boiling water onto their frozen windscreens its not often they shatter but it takes that kind of sudden temperature fluctuation to shatter a pane of glass.

My substrate is 7 inches thick and then slopes down to 2 inches on the other side.


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## james67 (Jun 28, 2008)

yep. i just recently threw one in the trash. its just not worth the risk IMO.

your also not talking about a windscreen which is made of 2 pieces of heat treated glass layered over plastic film. your talking about a single pane of tempered material. 

aquarium heaters use a buffer of air, or other material in the tube to prevent failure, as opposed to heating the glass that encases them.

as for the theoretical scenario i proposed, the heater would be unlikely to evenly heat the volume of water before reaching its full temp (well over 100F, just put your hand on one thats running. if it feels even warm than its higher than your body temp / so easily over 100 degrees)

james


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## Pumilo (Sep 4, 2010)

My son had an under tank heater in his Kenyan Sand Boa tank. It cracked the glass. I have worked with glass for a living for over 20 years and glass CAN and DOES crack in excessive heat. In fact it has a very odd pattern when heat cracks glass. Here is a pic of that crazy heat crack pattern. I see it fairly often when people use black curtains, black blinds, of apply that crappy 3m tinting on the inner pane of an insulated glass unit.
I'm going to go with James and say that an aquarium heater is the safest bet. I have heard people say they have had success with mounting an under tank heater on the back wall but I have NOT tried that personally. An aquarium heater is safest but I would use it with an external, separate thermostat.


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## Mountainfrogs (Jan 23, 2012)

Any suggestions on an aquarium heater. The one i currently have is not fully submersible. Also what about the aquarium gravel heaters?


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## ghutch0203 (Jun 13, 2010)

Do you have to have a heater? Your safest route would be to not use one at all. If the room temp is controlled you can control your viv temperature. Is this viv in a room the gets to cold? If so just get a small space heater to boost room temp. My frog room is 72 and all my vivs stay mid to upper 70's. Just a thought.


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## Pumilo (Sep 4, 2010)

ghutch0203 said:


> Do you have to have a heater? Your safest route would be to not use one at all. If the room temp is controlled you can control your viv temperature. Is this viv in a room the gets to cold? If so just get a small space heater to boost room temp. My frog room is 72 and all my vivs stay mid to upper 70's. Just a thought.


Agreed. I use an electric, oil filled heater controlled by a Ranco ETC.


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## ghutch0203 (Jun 13, 2010)

My frog room is about 12 by 25 and I use two seven foot cadet soft heat hydronic baseboard heaters controlled by a digital tstat on the wall.


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## Mountainfrogs (Jan 23, 2012)

I don't have a frog room, my tank is in my living room. I live at 8500' elevation so the winter gets pretty cold and I heat my home with a pellet stove. I don't think my wife would appreciate the cost or look of a space heater in the living room. I keep my home at 70 degrees in the winter but at night it can drop to the 60's easily. Keep in mind this tank is for red eyed tree frogs so it will be vented and will not stay quite as warm as a dendro tank.


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## parkanz2 (Sep 25, 2008)

I'm not familiar with the husbandry requirements for RETFs but a short term drop into the 60s is typically nothing to be concerned about with most darts to my understanding.


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## Ed (Sep 19, 2004)

With respect to RETFs, have you considered using a fan to circulate the air instead of having to have ventilation with the room? With respect to the under the tank heater being connected to a dimmer switch, this is not ideal since the thermal needs of a tank as it can't adapt to the thermal changes the way a programmable controller does (I use programmable controllers with various animals so I can deal with temperature fluctuations (since my basement gets down to about 45 F in the winter). As Doug noted heating pads can crack the glass since where the pad contacts the glass warms and cools at a different rate than the glass on the inside of the enclosure. Water over the inside surface increases the length of time required for the two surfaces to equalize in temperature (since water will be conducting heat away from the inside surface) and can create a higher risk for cracking. The fact that it isn't on the packaging doesn't mean anything.. Typically those warnings are the result of a lawsuit and part of the settlement (which is why as an example, my snow thrower came with warning to not use it to remove snow from roofs..) 

If you could drill the tank you could put in a sump and heat the sump and recirculate the water into the tank which would solve a lot of the problems but you are going to have a lot of condensation on the glass reducing visibility in the tank. 



Ed


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## Mountainfrogs (Jan 23, 2012)

I think what I am going to do is setup the tank and run it for a few days to see if I need an additional heat source. I may not need the heat source. My dual t5HO light ballast produces a bit if heat by itself. and it will be directly on the screen top.


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## Enlightened Rogue (Mar 21, 2006)

I`ve been usuing under tank heaters for years and never once did I have a problem. I never go a winter without them. They don`t get anywhere near as hot as most people say. It takes 3-4 hrs. to heat my tanks a few degrees. The water in my false bottom stays about 75-80 degrees and it keeps my humidity up to 75-85%.
As long as you have enough water in the bottom I don`t see a problem. just make sure the heater is not to big or small for your tank.

John


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## Judy S (Aug 29, 2010)

Ed said:


> With respect to RETFs, have you considered using a fan to circulate the air instead of having to have ventilation with the room? With respect to the under the tank heater being connected to a dimmer switch, this is not ideal since the thermal needs of a tank as it can't adapt to the thermal changes the way a programmable controller does (I use programmable controllers with various animals so I can deal with temperature fluctuations (since my basement gets down to about 45 F in the winter). As Doug noted heating pads can crack the glass since where the pad contacts the glass warms and cools at a different rate than the glass on the inside of the enclosure. Water over the inside surface increases the length of time required for the two surfaces to equalize in temperature (since water will be conducting heat away from the inside surface) and can create a higher risk for cracking. The fact that it isn't on the packaging doesn't mean anything.. Typically those warnings are the result of a lawsuit and part of the settlement (which is why as an example, my snow thrower came with warning to not use it to remove snow from roofs..)
> 
> If you could drill the tank you could put in a sump and heat the sump and recirculate the water into the tank which would solve a lot of the problems but you are going to have a lot of condensation on the glass reducing visibility in the tank.
> Ed


 did they also have a warning not to use your hands to remove obstructions?? That is hilarious...


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## Ed (Sep 19, 2004)

Enlightened Rogue said:


> I`ve been usuing under tank heaters for years and never once did I have a problem. I never go a winter without them. They don`t get anywhere near as hot as most people say. It takes 3-4 hrs. to heat my tanks a few degrees. The water in my false bottom stays about 75-80 degrees and it keeps my humidity up to 75-85%.
> As long as you have enough water in the bottom I don`t see a problem. just make sure the heater is not to big or small for your tank.
> 
> John


I've seen it happen more than once.. both with tanks that had water in them and ones that were dry (I just tossed out a 20 long, that I use for leopard geckos since the pad fractured the bottom). 

Ed


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## Pumilo (Sep 4, 2010)

Enlightened Rogue said:


> I`ve been usuing under tank heaters for years and never once did I have a problem. I never go a winter without them. They don`t get anywhere near as hot as most people say. It takes 3-4 hrs. to heat my tanks a few degrees. The water in my false bottom stays about 75-80 degrees and it keeps my humidity up to 75-85%.
> As long as you have enough water in the bottom I don`t see a problem. just make sure the heater is not to big or small for your tank.
> 
> John


John, I have no doubt that if you say it's worked for you so far, then it has. I'm not saying that an under tank heater WILL crack your glass. I am saying that it certainly has the potential to do so. I have seen it happen with my sons viv. As indirect, circumstantial evidence, I replace maybe a half dozen to a dozen heat cracked windows every year. During my 20+ year career as a glazier that's pretty easily 200 heat cracked pieces of glass through my hands.


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## Mountainfrogs (Jan 23, 2012)

like i said i am going to run the vivarium for a few days and monitor the temps once i get it all put together then decide the best route. Tonight i put the coir on the foam so we will see what happens here in a few days . I do appreciate all the input.


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## Pumilo (Sep 4, 2010)

Mountainfrogs said:


> like i said i am going to run the vivarium for a few days and monitor the temps once i get it all put together then decide the best route. Tonight i put the coir on the foam so we will see what happens here in a few days . I do appreciate all the input.


Sounds good. Hopefully you won't even need anything. Once you start a thread, though, it's up there for everybody to see so the debate often continues long after you have decided on your answer.


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## Mountainfrogs (Jan 23, 2012)

It's healthy to debate. I don't mind


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## Ed (Sep 19, 2004)

Pumilo said:


> Sounds good. Hopefully you won't even need anything. Once you start a thread, though, it's up there for everybody to see so the debate often continues long after you have decided on your answer.


*First law*: The velocity of a body remains constant unless the body is acted upon by an external force.http://www.dendroboard.com/forum/#cite_note-2


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## vaaksi (Feb 6, 2012)

I bought an ExoTerra heat cable (15W, 11,5') which says it should be used under or inside the terrarium and on glass terrariums only. It also says it's not waterproof, so I placed it under my glass terrarium following the safety instructions on manual.

Are heat cables also dangerous to place under a terrarium? Should I take it off now?
It gets very cold in here at winter, and we can't control how warm our apartment is, so I need some kind of heating. Aquarium heater is not an option because my terrarium does not have a false bottom.

Finnish www-sites suggest heat mats and cables placed under terrariums as a heating source to frog terrariums, so this was all new information to me.


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## mad6291 (May 28, 2012)

Has anyone had the heat cracks happen on a frog tank?? One huge difference between the examples I've seen given are that the animals the UTH were used in conjuction with were desert type species that require a high temp and usually dry or I should say drier conditions than PDF's. I think this fact may be a huge difference as a previous poster had stated that the water would equalize the temps as they rise and the glass would not suffer major temperature fluctuations but a emore gradual increase. It's when the heat is trapped or there is a major fluctuation that I have experienced crack glass. I am thinking a false bottom with a generour amount of water would/should be fine. What's your guy's take?? Appreciate the input.


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## Ed (Sep 19, 2004)

mad6291 said:


> Has anyone had the heat cracks happen on a frog tank?? One huge difference between the examples I've seen given are that the animals the UTH were used in conjuction with were desert type species that require a high temp and usually dry or I should say drier conditions than PDF's. I think this fact may be a huge difference as a previous poster had stated that the water would equalize the temps as they rise and the glass would not suffer major temperature fluctuations but a emore gradual increase. It's when the heat is trapped or there is a major fluctuation that I have experienced crack glass. I am thinking a false bottom with a generour amount of water would/should be fine. What's your guy's take?? Appreciate the input.


 
See this post http://www.dendroboard.com/forum/pa...under-tank-heater-placement-3.html#post693998 

Ed


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## mad6291 (May 28, 2012)

Thanks Ed, but that is one such example I am referencing. You mention your personal experience with Leopard Gecko's, which I can see happening. You also say you have "seen" this happen with tanks with water. If I may ask, how much water was there, and was this for frogs?? Was the UTH kept on a therm or rheostat?? Was precaution used and the occurance was simply something that could not have been avoided?? I hope I don't sound smug, but I would like to learn from your experience and judge for myself if it is worth the "risk". I apologies if you are offended for me asking about the experience. Cheers
-Mike-


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## Ed (Sep 19, 2004)

In a long history of working in institutional settings (zookeeper), pet store, and private keeper, I have seen in all conditions broken enclosures that had false bottoms, thick gravel layers or other materials in which all of the "space" was filled with water and I have seen all three of those types of enclosures suffer glass failure due to heat tape, under the tank heaters (with and without rheostats (and I have also personally also had heat tape hooked to a thermostat (with an inline rheostat) melt not only the plastic sweaterbox but the pvc shelf under it) and ignite the bedding in the sweaterbox. 

If you set up a glass tank and fill it with several inches of water and place a under the tank heater (of any sort) onto the tank and turn it on and watch closely, you will under close observation note convection currents from above the heat pad inside the tank. Not only are you getting a temperature differential as you move from the heat source along the glass, you are getting one through the thickness of the glass as the water cools the interior surface of the glass..... 

A rheostat and/or a thermostat doesn't prevent failure or localized hot spots which can be much hotter... It may reduce the risk but it certainly doesn't eliminate them...


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## mad6291 (May 28, 2012)

Thank you Ed, that's good information. Is it safe to say you would also suggest not side mounting the heat pad as well?? What would you recommend as a safe option short of heating the entire room?? Thank you again.


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## Ed (Sep 19, 2004)

If you can set up a sump with an inline pump, you can heat the water in the sump which in turn is piped into the tank, evenly heating the glass surfaces. Alternatively if the tank is on an enclosed stand, you can heat the air volume under the stand which in turn will more evenly heat the tank. The goal is to heat the tank as evenly as possible. 

Ed


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## mad6291 (May 28, 2012)

Seems a false bottom with an UTH would do just that. Looking at some old post: Dendroboard > Vivariums > Parts & Construction 
Any issues using an UTH with a false bottom? 

In the conversation that seemed to be the understanding as well. I agree with them that the water layer would serve as a buffer for drastic temperature changes and care must be given when changing water as to not drain the water to a dangerous level. Care must also be given with the breathing of the device so heat is not trapped. But with that, a suitable, if not, improved habitat can be maintained in cooler climates. I do thank and respect your input. Much appreciated


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