I use just plain fluorescent lights on the display enclosures. I have 2 that are interior mounted and two exterior mounted. The exterior ones give off no heat to the enclosure to speak of the interior ones do heat the ambient temp some but not much, about 1-3 degrees depending on how efficient the enclosure it. One of mine is very efficient heat wise and holds 3 degrees from the light the other is not as good and only hold one. A tank is less efficient that mine (I have 2 tanks too) and I'd guess they would not heat much (at all) with a fluorescent light on the top. This one is one of the interior mounted ones.
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