You can keep balas with tinfoils and still have all the fish have fat stomachs at feeding time, it all depends on HOW you feed. I feed frozen brine shrimp, the tins will grow faster so as they get bigger They cannot get as full stomachs as the balas at a smaller size because the food is getting to be too small for the bigger tins. Pour in some frozen brine shrimp each 2 minutes and watch them all eat the balas tummys will expand doing this, and keep growing, dont put all the food in at once, every 2 minutes put some more in the tank. When I am done with the shrimp I put in some cut beef heart to finally make the tins tummys bigger and also give the balas some of that too.