I've always had an aquarium where I have rescued tropical fish from over crowded tanks and/or people moving and can't take them to their new location. I actually have a full house of rescues of 2 rescue dogs and one rescue Leopard Lizard.
I have a tropical aquarium with a 1 Three Spot Gourami and 2 Denison Barbs. All have been rescues and all are friendly in my community tank.