You need a bunch of trained goldfish who eat the flakes already. Then add the shiners and they will figure out that it is food. I have about 25 medium shiners on goldfish food right now and about 5 goldfish with them in a 30 gallon bait tank for my pet bass.
Do not use a heater with them...ever. I used to keep them with full ice cover...and the liked it. I would feed fatheads algae flake. A nice gutload as well as general care food for them.