My pet gerbils, hamsters, and rats, and now the feeder mice, as well, eat Harlan Teklad 2018 lab blocks. They're something like $15-25 for 33 lbs, depending on where you buy them, and they're really good quality food. I supplement the mice's diet with *very* high-quality dog food (Innova EVO) for the extra protein and fat they need when pregnant or nursing. They also get grain, dry and fresh veggies, and some table scraps, just like the pets do. I figure healthy, happy mice will make healthy, fat pinkies for the baby snakes.