I wonder if anyone can help.... We have 3 black mollies, 3 balloon mollies, 3 guppies and 1 Platie. One of the black mollies for the past week is looking thinner, weak and is swimming with his body and tail slightly drooped. He is spending more time in the bottom of the tank (not on the gravel, but swimming low), he is still feeding, though its taking him more time to get to the top of the tank for food than the others. The balloon mollies were only introduced a week ago (similar time to the black one starting to look unwell), one of which was heavily pregnant giving us babies a couple of days later. We had the water tested last weekend prior to the introduction of the balloon mollies and all was well. In the last two weeks, we’ve also had an outbreak of green misty algae on the tank sides, but this is easily scraped away.. but comes back. Any suggestions on what can be wrong with our black mollie will be gratefully received!.