I just did my first water change for them. They are all now floating on the top, not dead, but didn't go after the snails I put in for them to eat. Do they not like water changes? I used prime before putting the water in. I stayed away from them, sucked from front of tank, they were in back. I hope they don't die. Just checked their parameters, all looks good. Are they that sensitive? They all dove at the snails I put in early today.