My Gsp and whats this?

[RobertTheNurse]

Hey everyone. I've had this GSP frag for about 1 month now. Opened up and started growing. Have it on its own island. Noticed over the last 5 days it hasn't opened up like it used to. Stays closed with the exception of a few heads opening. My nitrates were 25 and I've been trying ro tone down some GHA ive noticed on the sand bed...so im currently now gonna do 3 30% water changes over the next week. I did the first one yesterday with maintenence on my cannister filter. I removed all foam pads and now use filter bags to house media etc.

Today tested water

Nitrates 10 with salifert (2.5 when viewing from side and dividing by 10).

Noticed this white thing on the coral...i took a video with the whites on so you can see.

Any ideas? Should I take the frag off the rock and dip again?

1.025
78F
Phos 0.01 (or undetectable) using salifert
Ammonia 0

 

[Daddy-o]

cant see vid

 

[GeoSquid]

Possible tube worm/feather duster. There also looks like there might be sponge with the see through tube in the front of the video.