Two items spotted..

If you dont kill them right away then by the time you realize you should start killing them it will be too late. My tank was infested with them until i went on a mission and was killing like 50 a week. I cant get them under control because they are in places i cant reach. I kill whatever i can reach but there are still hundreds i cant.

 

Sounds like you are taking about aiptasia (glass anemones) which will spread and "take over" your tank. I know by looking at the second picture that that is NOT aiptasia. Majano Anemones do not spread like wild fire to my knowledge nor do rock anemones which are other common hitchhikers. I am still thinking that green one is a bubble tip... looks like a mini-version of my gbta.

Heidi

 

Majanos spread just like aptasia only difference is peppermint shrimp will take care of aptasia but not majanos. I had issues with both but a few pep shrimp got rid of all the aptasia in my tank.

 

they spread very quickly. they took over one of my mushroom rocks and my mushrooms rarely fully open anymore because they get stung if they touch them. Ive used aiptasia x and it seems like they just multiply when the come back. they are a pest if you ask me

 

take out the rock, use a lighter and burn the suckers until they are completley gone, even the base of the majano can still contain spores, regrow itself and cause an epidemic.