So I’ve had 2 clownfish in my tank and every fish I’ve tried to put in there they have died and I’m pretty sure they killed them maybe just the black one she’s kinda aggressive. I know they can be territorial if I put them in a breeder net for a bit and add another fish to the tank would that make them less territorial or is there another way to do it, or should I just let them be the only fish in the tank. It’s a 20 gallon Waterbox.