what is that?

Hi everyone , I just got a bubble tip anemone for my tank and noticed this weird thing moving next to it while I am acclimating. Does anybody know what it is ?the arms also move

I posted this crab on Reddit and got multiple suggestions, there’s a little bit of an argument in the comments. What is this crab. He is at least 3 years old, though he was this same size when we got him. He lived with a mantis shrimp and some fish; also some soft coral but never did any...

Alright I need some help identifying this thing. It's a white fuzzy ball looking thing. Riding around on my snail. Any help is appreciate it.

Should I be worried? I’ve had my tank -cycled and running for about 18 months now and just two or so weeks ago.. I began to notice this growth. (I also haven’t added anything new in months, so why now?) The color is neat, but I’m worried it’s a pest to take over if I’m not careful!

Hi, I’m new on reef tanks, I recently started 4 months ago, water already cycled have a little bit of diatom and I have four hermit crabs, however I saw something weird growing from the back of my aquarium can anyone tell me what it is?

Does anyone have any idea what these are, or if they've even got a name? Thank you guys!