snail parasites

I’ve just bought a pyramid algae snail (tectus snail) from my LFS, i put it in my tank and i’ve come to realize it has this weird looking thing on it shell. Whatever it is seems to retreat quickly back into a hole in the shell when i move the snail when it feels endangered. can anyone help me...

I have something growing on the shell of my snail. It has little tentacles and I have seen it pull the tentacles in. I made a picture to try and capture what it looks like. Does anyone know what it could be ? And should I be concerned?

I was doing a water change and noticed that there was some parasite in my frag sized green stare encrusting polyps, so I performed a coral dip with iodine twice and tried to scape off as many parasites as I could. After dumping the dirty water in the sink, I was horrified by what I saw and took...