I have searched everywhere trying to find out what this is. It came on a small piece of LR from my lfs. I am quite new to sw and reefs. The closest match I think I have found says this is posionious to humans, but the blue or green variety is the most deadly. I do apologize for my ignorance, but thank you in advance!

I was thinking about adding an urchin to my tank but i have heard that urchins will eat coralline algae. Is it worth having them in there as cleaners or will they do more damage than they are worth. Almost all my rock is completely covered in coralline of different colors and i dont want it to be damaged too much.

so i bought a mexican turbo snail from my lfs and this was growing on its shell. any idea what it is?

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So I recently started my own tank, growing up my dad had a 200+ gallon tank and it was stunning, so I recently moved out and wanted to have something to put money into. I bought a 20 gallon tank about 4-5 months ago and stocked it with some live rock and sand and some hermit crabs to look at. So it's been 4 months and i decided to add some Coral and a Damsel. When i was at the local shop they had coral frags for sale for 20 bucks and one of them was what looked like an anemone but in a coral? I'm not sure what he is, he dosent move around the tank like an anemone he just stays on the piece of coral and when he wants to he can pretty much completly dissapear inside of the coral and i can't see him.

I have a 30 gallon tank ive been running for a few weeks now(first corals added 2 weeks ago). I have a finger leather, a zoa, a green star polyp, and a chattering polyp. within the last couple of days the polyp has been shrinking and moving a lot less and some of the polyps have started to turn white and fall off. All of my levels are fine but it continues to get worse. The piece is a plug with two seperate frags on it and only one seems to be affected. Should i cut this one off and try to save the other? I also just fragged the finger leather could this add to the problem if it is still releasing toxins i held it in a seperate tank for a day after i fragged it?