mate something like fire tail gudgeons or the most widely used feeder fish because they can handle so many water conditions but will breed only in outside ponds and dont have a quick growth rate if you want a fish you can breed at a quick pace you might look at a non native species like mollies or guppies which are live bearers and will grow at a lot quicker pace though you will need to breed alot to be able to supply a growing fish enough food, why dont you just freeze some fish? barra will still munch on a dead meal aslong as it looks natural