I also battled cyano, still dealing with it, but it is much less of an issue than before. it was so bad before i came very close to scrapping the whole tank, but.....
what I did (deep breath):
1. added new PC Bulbs
2. added more water flow
3. did more water changes, siphoning away cyano and detritus from the sand
4. cut back on feedings = less nutrients in suspension
5. added macro algae to my sump/fuge for nutrient export
6. added a two little fishies Phosban reactor. 2 thumbs up for this simple inexpensive reactor. i think this really helped
7. cut back on photoperiod from 12 hours per day to 10 hrours per day
8. added a powerfilter with carbon only.
So, yes, it was a battle. but it is now at a manageable level
good luck!