Bryopsis?

I really haven't added anything new in the past month and this is in my sump.

If it's bryopsis then my plan of action is to drain the sump and clean out the middle section manually... Or I could just turn off my sump light? I don't want it to die off and end up in dt so suggestions help!

 

Hard to tell, for me that is. If it is good luck. My 29 gallon was over run by the stuff. Only thing that stopped it was removing one rock at a time, pulling off the loose stuff and hosing it down with hydrogen peroxide. Three days later the CUC was chowing down on the dead stuff.

I don't know where it came from.

I can only suggest that when cleaning it, don't let any loose stuff get into other compartments or it will spread. That was my experience at least.