My two black mollies at first were very active. Back when there use to be three, they would swim all over the tank and explore their environment. Now, long after the third one died, they just sort of hover in place. At first they would sit in one place towards the top or in the middle, now they've built a habit of just sort of resting at the bottom on the gravel. But they don't really just rest there, they pound their fins and are working pretty hard just to stay in one spot. My Red Wag Platies are okay, they swim all over the place. It's just the mollies. Weird...does anybody have any idea how to get them moving again? What if I added a few more mollies? Could I get them to school? They live in freshwater, no salt(decided not to use salt all the time), 20 gallon tank. I still need to get a new test kit, but the water has no ammonia or nitrites in it. That, I am certain of.