[HeyPK]

It may be a caddis fly larva. Most of these have a little "house" made of bits of leaves and other junk glued together that they carry around like a hermit crab carrys around its shell.

 

[HeyPK]

Hand removal is best, or a large hard-mouthed cichlid. A crayfish would get them, but then it would probably eat the plants for dessert.