ive got several on bits of wood in my tank, and yes they perish and come off over a long period of time, they dont do any harm and you could replace them now and then to stop them doing that. The fish dont even notice them, di
i have some in my endler tank holding sponge to the filter so the babies don't get hoovered up. it does rot like everyone says, i replace mine when it starts to get baggy or starts to look ewwy, has yet to bother the fish.