heating methods for 18x18x24 - 2 white's treefrogs

[Mentat]

I use a 100W ceramic type heat emitter to warm a 20 gal. ABF tank and it does a good job. Do make sure you have a dimmer (my Fluker's Dome came with it) or a rheostat controller to adjust the energy output as required. Insulating sides will help; but most heat escape enclosures through the top. Might consider ways to diminish heat loss there too.