#pest ? critterid

Ya’ll, what are these?? This tank also has strangely large amphipods and an over abundance of them. This tank also has 2 pincushion urchins that refuse to eat the green algae in that particular area. Lots of amphipods and weird worms living in green algae, never seen before. No wrasse in this...

Can someone help identify what this is? There is quite a few of them in one corner of the tank but this one was easier to get a picture of.

Need help anybody know what this is?

Hello, Yesterday I noticed these things, marked up in the image, in my tank. I tried poking them and they close up and retreat to the hole in the live rock. Can someone identify them? and tell me whether I need to do something about them? N.B. I always dip my corals in Seachum dip, and I don't...

Anyone know what these are and if I should/ how, get rid of them?? I do a 25% water change about every 10 days but doesn’t effect them at all