I've never heard of fry or goldfish eating roots, though they do like hiding in it. They usually only eat what they can fit in their mouths, so if you wanted to try cutting it up or something, but that seems like more trouble than it's worth. They might not even eat it actually, even cut up. If you really want to feed them live anything, you should probly culture them some food. I'm going to start culturing food, some worm probly, so I'll keep you updated. ^^