When I first got into this hobby back in Feb., I bought 6 Black Mollies (along with a lot of other fish). All the Mollies died. I bought 6 more. Again, all died except one. Then a month later I started getting molly fry. Then I got a lot more fry. I raised them, gave them to the LFS. Then I got more fry and the same thing...ran to the LFS. This continued until I took the large female to the LFS. Now the offspring are filling my tank with fry. I've had to isolate all the Mollies to a separate tank. There's no end to this. How do I turn this off?