You do not need to buy a seperate tank for each of them, but you will need to seperate the males once they show signs of aggression, some people use mason jars, tuperware, tanks with dividers, pet carriers ect ( lee's kritter keepers is what I plan to use). As long as you will do regular water changes and can find good homes for them, you have lots of options. Be sure to do your research and stock up on supplies before you spawn, it takes time, preperation and supervision to spawn and raise fry, but its worth it and always exciting.