Looks like a snail/slug. Has a shell like a limpet but can hide under it all. I'm going to try and get a video of it. I've had my tank set up for 6 years and never have I seen this. It also moves very fast
It was all up on a zoa colony. I couldn't tell what it was since it had stopped moving and then I poked it with the tip of my feeding baster and it started to move fast. Luckily I was able to grab it
I have these and I will see them once a month. Each time it has doubled in size. But I’ve certainly never seen one that fat before. It must eat a ton in your tank.
Definitely stomatella I have white brown and black ones in my tank. I've seen them spew out their reproductive slime all through my tank. Super neat. Great for cleaning they are just browsing through your zoa not eating them.