not a clue, but the quantity of water is quite a bit. Definitely over 10 gal
. Its an old terrarium Ive converted into a watergarden/aquarium. (That is, its mostly plants but there are a few fish in it).
I used to have a small 50W heater sort of laying horizontally along the bottom, and it worked, but it kept sinking into the sand and eventually actually slightly melted the rubber support thingie that was sort of holding it up. Besides it was tricky to set up because of the way it is planted. Figured I should probably get it out.
I need it because both the plants and the fish I have in it like the temp to be a little warmer than the 21deg. C that it currently is, and also to create a slight convection current.
I seem to recall someone somewhere mentioning making a heater with sand and glass, but I don't remember the forum I read it at (and Ive run searches at all the ones I usually go to).
I would definitely prefer something I can "shape" for the location.