One part of the project was to make a cheap flea trap. This trap only uses a few drops of soap. Using lots of dish soap would create a similar affect, but soap costs more than using water.

Again you do not need a heat source, but you do need a light source. But if you are catching fleas everywhere you may need to thoroughly clean your room. The traps you are using are working from the fleas randomly jumping inside VS using a beacon to get all of them out of your room.