What is this green thing??

[Gordi]

Hi, noticed this green plant-like thing on the back of a snail!
Any thoughts????

 

[WheatToast]

That’s the ultra-rare Neomeris, a calcified, green macroalgae. Usually, it dies in captivity (disintegrates into sand), but when conditions are right, it can become invasive. It is also otherwise known as Caterpillar weed and Finger algae, but I like to call it Alien fingers. I wish you could give me some, but you live in the UK, and I live in the states ;Inpain.
https://www.marineplantbook.com/marinebookneomeris.htm
https://www.livealgae.co.uk/green-macroalgae-species/marine-macroalgae-neomeris-annulata

 

[eggplantparrot]

That’s the ultra-rare Neomeris, a calcified, green macroalgae. Usually, it dies in captivity (disintegrates into sand), but when conditions are right, it can become invasive. It is also otherwise known as Caterpillar weed and Finger algae, but I like to call it Alien fingers. I wish you could give me some, but you live in the UK, and I live in the states ;Inpain.
https://www.marineplantbook.com/marinebookneomeris.htm
https://www.livealgae.co.uk/green-macroalgae-species/marine-macroalgae-neomeris-annulata

Finally got a name for it. I had this stuff growing out of 2 spots on this one piece of live rock I have. It would die back after reaching nearly 2 inches and would sprout new ones.

 

[Gordi]

So it's not a bad thing???

 

[Udest]

nope macros are a really cool thing if you get em better if you can keep some of the cooler ones though.