i know this is an ancient thread. i have recently eradicated completely a terrible cyano outbreak. in all my research on various forums, including this one the most, it is amazing how many divergent opinions there are on the topic of getting rid of cyano. i do understand that every tank/situation is different, and with so many varying parameters it is difficult to assess what works and does not work.
For me...and it may be coincident...it was changing RO/DI filters and media, adding low micron filter pads (50,100 and 200 changed daily) and stopping GFO.
I siphoned it off sand, but this is imperfect process. It was all over my rocks and disappeared completely from them, so this makes me believe brushing and siphoning are not primary eradicators.
My phosphates are zero to 0.03ppm since stopping GFO. So there is clearly a trace of phosphate in the water column.
I went blue/royal blue exclusively on the lighting (21,000K) - no help.
I slowed feeding - no help.
I did massive regular water changes - no help.
I added chemipure, carbon, and purigen - no help.
Continued fuge and algae scrubber - no help, although i did increase flow rate thru fuge at the same time as the eradication was taking place.