i just watched a few videos regarding this tank.there is no doubt in my mind that you could place a heater in this tank through the feeding hole.if you want the feeding hole to close you would have to mod it with a drill.the two major questions that remain unanswered are these. what happens to the waste before the plants start to grow?how long into the growth cycle before the plants are effectively using up the waste? i encourage anyone with this system to do a series of param tests and let us know the results. i was not able to see the actual directions for myself,so i am curious. they do include some sort of betta bath chemical along with some sort of bacterial colony starter,some seeds,rocks and a small pump.i am really curious about this system.i think it would be a really cool gift for my mother,but i would like some feed back first.