If you already are using an RO
unit then you might want to check your water turnaround.
What is the turn rate on your tank? I see you have a couple of powerheads, having at least a 1
water turnaround inside your tank might help with cyano
. Is the algae all around your tank? Or is it in some spots? If in some spots, then you might have low water flowing there or even dead spots where cyano
Using agents to reduce PO4
is ok but it would be better to find the root of the problem in the first place.