Help me identify this.

[germo]

This stuff started on the glass as little flakes. It blows off my rock work fairly easy but is a bothering me because I don’t want something to take hold. I just finished battling GHA for two months. Any identification and advice would be appreciated.

 

[germo]

Also I need to clean my glass so please excuse. All parameters are with in normal ranges. Temp stays 78 F and Salinity is 1.026. Lighting is AI 16hd and I’m running the Troy Rogers setting.