I did have a clam Mysteriously dissapear last month. I've only seen this snail at night and last night was the first time. I haven't added anything to my tank in over 6 months...Coral wise.....Interesting. said:You might try posting this on Dr Ron's forum on Marine Depot to see if he can give you an ID of some sort. That color pattern seems to be pretty distinct, but a shot of the hole it pulls back into might be needed for a definitive ID.