Bleh, you want to stay away from the pet store mess. It has corn(cancer causing because of the mold) and alfalfa(not digestible), and tons of little seeds that are just fattening.

It's really easy to bulk up a mix by using 2-3 boxes of kashi Go Lean and Crunch, Oatmeal Crisp, cheerios, blueberry morning, other granola cereals, dry brown rice, dry lentils, dry split peas, dried pumpkin seeds, 2-3 bags of tri colored pasta(I use wacky mac), wheat pasta twirls or whatever, black oil sunflower seeds(small amounts), dry old fashioned oatmeal(the whole big container), dry-roasted NO SALT in-shell peanuts, etcetc.

I make my mix up in 50-60lb batches and it might cost me $50? each time. Lasts a good solid 3.5-4 months for 25 rats, with lab blocks every 3-4 days(make sure they're not missing any nutrients). I also use Wellness Senior dog food(only has 17% protein and low fat).