i assume youre talking about a rheostat. those are halfway decent if the temps of the entire room are at a constant, but arent very good if not. i would recommend getting a Helix thermostat. they are a bit pricey but you can find them on sale every once in awhile (i paid $130 for mine). they can control up to 3 heaters at the same time to one temp. now here is what they will do exactly (since i had thought something different):
3 tanks with heaters set to 88F. the heaters will all kick in and have relatively close temps (depending upon depth of substrate, thickness of glass, etc)unless you have somehow managed to get all 3 tanks at the same temp. now the helix will keep the heaters going at the same voltage throughout each tank until (through outside heat sources) the temps of the tank go over 88F. the helix will then shut off the heaters to all 3 tanks. so if youre thinking of buying a thermostat and assuming it is going to shut off after a certain temp and kick up the juice if it drops below a certain temp, youre wrong. i dont know of anything that does that. btw, the helix bases the temps on a single probe supplied with the thermostat that is set directly into a single tank. so basically it is best to have a constant temp in all tanks if using the helix for multiple enclosures. because if the temps in all tanks are not at an even or relatively close degree, then one tank might shut off at 88F and another shutoff at 90F and another at 86F. hope this helps.
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