I have never cared for a fish. I had a tenant move out and abandoned a Dwarf Gourami in a dirty, algae covered tank that was unplugged without a heater or filtration. I took the fish home with me instead of leaving it there to die. I bought him a 10 gallon tank that he has been in now for over a week. He has not been active since I brought him home. He eats. He mainly stays at the bottom of the tank. I brought home 2 more Dwarf Gourami on Saturday and the first day he was following one of them around. Now he hardly moves. He is still alive but seems worse than before. Anything I can do to save him?