You just take clear plastic box deep and square (i have some laying around from candies and veggies and what not, tie wires to its sides and make hooks at the ends. Secure it inside of your tank hooking it on the front or side wall. For it to have water exchage with the main tank, make some holes on the sides - better than on the bottom. Hook the contraption on your tank's wall and it will be like compartment inside your tank with all the perks - filtration and temp exchange. Put buggers inside -they will be happy. Once they pick up some confifence and weight you can let them to swim with adults. If you have big loose java moss,they make it their headquaters.
It's realy very easy to home made it.