Anyone know what these are?

[ReefGrrl]

I'm cycling a new 20g nano with sump. I used dry Marco rock and have been ghost feeding every day and adding 30ml of Microbe Lift Special Blend on alternate days. Today is day 13. I had the lights on for the first 5 days and then off since then, only turning them on to document what was happening. No detectable nitrite, a bare shadow of colour for nitrate, nothing measurable with the kits I have.

Yesterday I noticed these small white circles have appeared in the areas of diatoms - they are the actual rock and can't be scraped off. When I scrape, it's the diatoms that are removed, not the white areas.

I'm hoping its bacteria growing and consuming the diatoms but I've never seen this before, and searches turn up information about only stuff that's removable, not this type of thing.

Any ideas? I have a better picture but I'm having trouble uploading that file - I'll try again.

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