i use New Life Spectrum Grow. it's in my mixture of foods(a baggy with a good number of different pellets in it. :D), and it's got alot of protein. frozen blood worms do, i think.
also, tail biting isn't anything to worry about. it used to stress me out, then i saw how happy Ichi is, since he chomped his tail super short, so i'm like "as long as he's happy, he can keep his tail short". but, that's just my view on it. don't let it stress you out. :3
if you can get tannins in their tanks, that may help stop their biting if it's stress-related. naturally dried oak leaves, decaf green tea, or Indian Almond Leaves will do the job. :3