Last night I turned off my return pump for a couple hours while I was feeding some corals and adding some top off RO/DI water. This morning shortly after the lights came on, I noticed these spots on my RBTA. Never seen this before. Anyone know what it is? Haven't seen anything picking at it or anything like that. Salinity 1.025, 0 ammonia, 0 nitrates, 0 nitrates, 8.2 pH.

