Make sure that they can't get in the filter dummy. I never had it happen to me, but I made sure that it never happened. It's easy to cycle a tank. Just as long as you don't add any more fish, then your tank should cycle soon. As long as your fry stay alive then, in my opion, your water is good enough. Fry need pristine water conditions to survive, so if they're healthy (along with all of your other fish) then your ok...for the moment.