Snails are beautiful, graceful and fun to watch...but nasty as all get out. I got some mystery snails awhile back to help control the algae and figured they could crawl in their shell if my shark bother them. Told they would not reproduce in freshwater. When they grew up..they started laying egg clusters, on the glass, behind my HOB filter (and this was a pain to clean up), no one said they would not lay eggs, just not hatch out those eggs. They became more of a mess maker than they were a clean up crew. I ended up rehoming the lot of them. So now I am looking for algae eaters that will clean and not mess and my shark will get along with.