white spot

[friendship1965]

Hello friends. What is it ? Hard white spot in the tank ( on the glass,Astrea Snail and others...) sometime clear with the razor blade but becoming 15 day later.

PH: 8.1 No2: 0 Salt: 1,023g/cm3 Temperature: 77F

Sorry for bad English !!
Thanks for helps.

 

[IowaBoy]

are you using live rock?

 

[friendship1965]

are you using live rock?

Yes , I have 3 small live rock and one Clove Polyp.
1 Tube worms.
2 Tiger Sand Conch.
1 Astrea Snails.
1 Cleaner Shrimp
1 Fire Goby
2 Blue Green Chromis

800 liter ext. filter, air stone protein skimmer and using 3 in 1 calcium, iodine, strontium, molybenum, magnezyum, trace elements and kh/ph plus.

 

[friendship1965]

Thanks AG1 for help to me. It is Spirorbid Worms.