Help ID snail hitchhiker

[reefbuck24]

Trying to figure out what’s attached to the astrea snails in my tank. Have been growing for about 6 weeks. They look like feather dusters but do not retract into their tubes. The tubes keep growing and now are over an inch long.

 

[Reefkeepers Archive]

Hydroids, you want to remove those as they can easily overtake a tank and can sting corals, @ISpeakForTheSeas may have some removal advice

 

[EeyoreIsMySpiritAnimal]

Trying to figure out what’s attached to the astrea snails in my tank. Have been growing for about 6 weeks. They look like feather dusters but do not retract into their tubes. The tubes keep growing and now are over an inch long.

Sacrifice the snail. You do not want these to gain a foothold in the tank!

 

[ISpeakForTheSeas]

I'm not sold on these being hydroids - this almost looks like early stage (pre-reproductive stage) Acetabularia (Mermaid's Wineglass) algae growth with the greenish tint and the little whorl of feathery appendages at the tips; I'm just not sure which species it would be, as it's hard to find good pics of juvenile specimens of this algae.

The images in these links taken together should give an idea of what I'm talking about:

Acetabularia | Marine Algae, Single-Celled Organism, Photosynthetic

Acetabularia, genus of single-celled green algae (family Polyphysaceae) found in subtropical seas. The algae are among the largest single-celled organisms and also feature an unusually large nucleus. Because part of one species can be grafted onto another, Acetabularia has been used to study the

www.britannica.com

Acetabularia, an unusual unicellular green algae – Inanimate Life

milnepublishing.geneseo.edu

https://www.researchgate.net/figure/Juvenile-adult-and-reproductive-morphologies-of-Acetabularia-acetabulum-This-giant-alga_fig4_8632137

(The pics are down a way on this last one.)

Acetabularia acetabulum Mermaid's Wine-glass,Mermaid's Cup

Acetabularia acetabulum is commonly referred to as Mermaid's Wine-glass,Mermaid's Cup. Difficulty in the aquarium: There are no reports available yet that this animal has already been kept in captivity successfully. Toxicity: Toxic hazard unknown.

www.reeflex.net

 

[reefbuck24]

Took snail out of tank today and physically removed all the stalks I could see with tweezers then dipped the shell in a peroxide solution for approximately 20 seconds and lastly brushed the shell with a coarse plastic brush. Hopefully i got them all but I have my doubts.