How to stop or atleast lower down the fin nipping?

hi i have a figure 8 puffer and it is nipping some of my fish fins. i dont have another tank to put it in and my dad said no more fish tank in house. i have a crayfish in one tank andgoldfish in another. should i feed him shrimp to trim his teeth (or snails.) i dont want to give him away. the other fish are gold gourami, silver dollar,dojo,knight goby,sa bumblebee cat, pictus cat and a dragon goby(temporary till i give him a new tank.) what should i do