I have started using hairnets to hold moss, pellia, etc. to rocks or driftwood. I have a small piece of driftwood, and I wanted to attach a small java fern to it. I wrapped the whole thing loosely with the hairnet, tucking the excess under the driftwood. Well, I came home to find one of my tiger barbs tangled in the hairnet, near death. He/she didn't make it, and it's my fault. It never occurred to me that one of the fish would get underneath, somehow. The fish was so tangled in the hairnet that I had to cut the net in about three different places, and still had to untangle it.