Aaaarrrrggghh....it is not a root

[MrMashashin]

ummmm it looks like one of those Tommato Worms. Nasty looking buggers

 

[Never2Bknown]

NO, NO! NOT a caterpillar! Definitely not a caddisfly. And certainly not something that you can find in your garden. It appears to be some sort of nymph, probably a cranefly; I will try to look it up for you to be sure. (I'm into aquatic entomology, so I would know a bit about this.)

 

[Never2Bknown]

Yeah, I looked it up. It's definitely a cranefly larva. Ugly, but not harmful to your fish.