there filter feeders um some mussles are rock boarers so once the attach to rock they boar through it until the rech the other side then they just make tunnel in the rock the dont really cause problems unless there zebra mussles then youll have millions of them.
If you look at the picture the shiny white part looks like a mussle shell i have mussles in my tank and thats what they looked lkike before they got there color so its definetly not a limphet the other white stuff is its foot and other things just holding on for dear life
well your idea of putting it ina fuge or sump is a good one cause god only knows i could be wrong too for all we know it could be a mantis egg or something rediculouse like that casue sometimes things arent what you thought they are