Algae ID

[ascaley]

I’ve searched everywhere, no idea what this is! It’s growing on rocks and on the back of the tank. It’s quite structured.

 

[LiLinka]

Looks to be ulva algae or commonly referred to as (lettuce algea) I would recommend some clean up crew to eradicate it before it gets to bad. I have had some good success with emerald crabs and hermits. Emerald crabs tend to pick at all algae's that have structure to them like ulva, bubble, hair etc. 1 emerald pet 20 gallons of water is recommended. Manual removal by brushing rock with a clean toothbrush or picking it off with tweezers are also options as well.