what would it be( No pics sorry)

[fishguyxd]

Well I have a bottle trap setup trying to catch what i believe is a little mantis
But my cleaner shrimp seem to thinkthe bottle is a cozy place too and have to be helped out twice already. Tonight i notice this little 1/2 inch spiny "slug" looking thing in the bottle and now trying to go back in. Is this what it could be it moves real slow and covered with little pointy thorns sorry no pics yet.