Identification Help: Odd circles forming on walls and floor

[dkegflorida]

I need help identifying these weird “circles” forming on my shark tank walls and floor. The algae seems to be disappearing in the area. I thought it might be caused by the aptasia eating nudibranch but I never see any day or night

 

[Sophie"s mom]

I need help identifying these weird “circles” forming on my shark tank walls and floor. The algae seems to be disappearing in the area. I thought it might be caused by the aptasia eating nudibranch but I never see any day or night

Looks like it could be early signs of coralline algae to me. But wait until others chime in, as I am no expert.

 

[dkegflorida]

Looks like it could be early signs of coralline algae to me. But wait until others chime in, as I am no expert.

The largest circle on the wall grew 4” in diameter overnight

 

[dkegflorida]

The largest circle on the wall grew 4” in diameter overnight

The previous circles are gone and now I have spiral like designs about 12” around.