Grind it all together. And again if necessary, to make it a consistent mix. Be sure not too feed more beef heart than your fish will eat, especially at first. Beef heart can quickly foul the water if left sitting. Always siphon out what your fish don't eat.
Live foods are another great option for feeding.
Live foods give your fish a walk on the wild side, and can get potential breeders in tip top shape. It is really amazing to see a listless fish come alive whem they first see the wiggling worm or whatever, rush over to gobble it down, and then look around expectantly for more. They do pose the disadvantage of potentially carrying disease, however, and live food should only be obatined from an absolutely reliable source. It has been tubifex worms that been prominently involved in the panic about disease transmission through food. Other foods have caused horror stories as well, but tubifex will always carry discussion.