Hi. I have a lot of fry piranhas, they're 4 days old now. I'm afraid to put them in the new tank that I have set up with my wife. When is the right time for me to move them? The tank where they are now has a lot of cotton like thing that's everywhere. Should I take them out? When can I do water change? Suppose to be it was the time for water change when I realized they're not behaving the usual. That's when my wife started searching what to do. Please help us cuz we know that not everyone is blessed with fry. Thank you guys in advance!