Looks like the same purple algae I get in my 180g and 32g tanks.
In the 32 its a combination of bubble algae and whatever the purple algae is. in the 180 its just the purple stuff. I get a thin layer of that on the rocks in the 180. in the 32 it covers everything!!
I suspect it is due to poor lighting quality. The 180 has a single LED bar light as this is a simple FOWLR tank. The 32 was intended to be a micro reef but has never quite worked out. The light on the 32 is this...
The SolaRay 4K Sphere LED Reef Light from Coral’s Coral would be a very interesting light with a novel form factor if we hadn’t already seen this exact light more than six years ago.
reefbuilders.com
I won this light in a contest on a live sale a while back.. Honestly, I feel a Kessil A360 tuna blue would do a better job.
In the morning when the lights are all on, I will snap a few pics to show you...