Right now this is a pilot experiment, and in this capacity there is the need to keep costs low and, hence, my attempt to build a control system (keeps costs low and I learn stuff, which I really love).
I suggest you get an old junk refrigerator to use as your insulated box (or build an insulated box). In the box you will need a large mass with good heat transfer to maintain stable temperatures. Maybe put a large container of water in the bottom of the box with an with some aluminum fins in the water sticking out of the water into the air for good heat transfer. Modify a aquarium heater such that the heater is in the water container and the thermostat section is in the box air section. The humidity should stay at ~100%. Just inside the box use a clear barrier (Plexiglas or clear plastic film) so the box door can be opened for observation without interacting with the atmosphere in the box.