Just to give you an idea I started with about 20-25 or so baby MTS and within a year I have harvested a little over 200 or so. MTS will multiply quick if given a constant food source. So in other words if you over feed there is a possiblity of them over populating your tank.
I don't believe they will need a heat pack, i've had some survive in a container of gravel that I was trying to dry out. So I would say they are pretty hardy.