What are these?

[Guy Cesario]

Started as one hitchhiker, now it’s a little group.

Help?

 

[James M]

Aptasia. Very bad

 

[Murica]

Destroy immediately. Peppermint shrimp, aiptasia x, berghia nudibranch, etc. Every removal method has its pros and cons

 

[Geebs19]

^+1. Get them out as soon as you can. They spread fast.

 

[ReeferJen]

Were you able to eradicate?