red slime?

[OCDP]

Agreed with rickjames. Also, up your flow to the areas it's growing on. Syphoning is your best bet for removal. I have heard turkey basting boiling hot water also "destroys" it and gets rid of it. I have not tried this though.

[crusty1]

Red slime was overtaking my refugium and getting everywhere in the DT as well. I cut back the photoperiod on the refugium to 12 hours from 24, and it nearly disappeared overnight.

[Snappy]

sounds like cyno, if all else fails a product called chemi clean works well but in my experience can bleach or even kill some corals.