[Witfull]

i have to disagree on several comments made here.

first, bryopsis does not require calcium to grow, Halimedia is a Ca demanding macro.

more importantly i highly disagree with cultivating a highly invasive algae anywhere in the system. due to sporing and fragmenting causing reseeding, why would you want it to be anywhere in your system?

as for the cynobacteria, that should be actively removed from the tank/sump as well. it is a great exporter of nutrients expecially PO4.

what i would suggest to combat bryopsis is to pull the rock, and in a bucket of salt water vigorously scrub the areas with a small wire toothbrush. scrub all growth areas clean. then in a separate bucket of clean salt water, rinse and flush the rock and move on to the next rock.

controling nuitrient input is paramount to battling any algae outbreak, along with blowing off the rocks to remove sediment that can fuel the algae. when fighting a serious outbreak, proactive tactics need to be taken. as stated above, physical removal outside of the tank is needed. to help control nuitrients via natural ways i would suggest chaeto as a macro to grow in a fuge. it is far less invasive and easy to control.