Rat food is ok for mice, I was the one that said that they have similar nutritional needs. Rabbit pellets can be added to the diet, but should not be used as staple diet as rabbits and mice have very different needs. Rabbits are cecotrophagous (or something like that) and they need a high fiber diet, while mice are omnivorous and benefit from some higher protein diet. Guinea pigs have a very different diet (I don't know exactly how, but I have read everywhere that it's very different from that of other rodents... specifically they need a lot more vitamin C... I don't know what else). Anyway, GP food should not be used for mice. Gerbil and hamster food are usually sold as the same. Gerbil food is supposed to have less fatty seeds (sunflower and pumpkin) but still most manufacturers sold them as 1. It is basically a seed mix. It is ok for mice, but it's low quality food for them (no matter how high quality it is for hamsters and gerbils, it does not provide the necesary nutrients for mice). Also, mice tend to be picky with the seeds and just eat what tastes good (sunflower and pumpkin) and leave the rest out. I think the best to buy for them is high quality lab blocks (mice/rat food) and add some veggies/fruits and maybe a bit of hamster/gerbil seed mix and dog/cat food or doggie bisquits. These last should be given as treats... not in enough quantities as to interfere with them eating their lab blocks... but enough to give them some variety in their diets.