what is this

[sansouci01]

Last night all my zoas and my birdsnest closed up for no apparent reason. Today I come home to find this on my zoas. All the zoas and birdsnest are on the same rock. Every thing else in the tank looks fine for now. getting ready to do a huge WC. All my parameters are good.
sal...1.025
cal...470
alk...9dkh
PH...8.1
temp 78
nitrate....05ppm

Don't want to lose my tank again

 

[Sniperhank]

Is say hair worms. Relative of spaghetti worms. Usually harmless and a sign of a healthy tank, can stress corals.


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[sansouci01]

Thanks Sniperhank.
Would this also affect my birdsnest? I don't see anything like that on it but it has closed up as well. Maybe not closed up but less polyp extension

 

[Sniperhank]

If they aren't seen in and around the coral the answer is no.