I got rid of cyno in my old tank years ago with small doses of the antibiotic Erythromycin, the form i used was some sort of fish medicine, can remeber the name. I had a horribble outbreak and got desperate, I added half a tablet, then another every few hours, once mass die off started to occur, I siphoned it out as it dies, followed by 25% water changes twice a day for a couple days, also ran with lots of carbon, it got rid of it for the remainder of the time I had the tank up and running, with no noticable side effects, fish.coaral, and inverts were fine. Most slime removers are simply dilluted antibiotics from what I've read, my method was more potent, but for a very short amount of time, plus the water changes and carbon quickly removed the dangerouse levels of the antibiotic.
I wouldnt call it a bullet proof cure, but it worked great for me, just plan ahead, and plan to dedicate the bulk of two days or so to the tank, remove all of it AS IT DIES, then start changing water and run lots of carbon, think I used a fresh batch every 8 hours or so....by the end of the week my tank never looked better, and ran cyno free for at least a couple years before I replaced it with a larger tank.
I tried the blanket in the dark method, and it camwe back in a week, you need to kill it all off, and elimiate the source of what was feeding it in the first place, the massive water changes, totaling to more than a total water change in a 48 hour period likely removed the growth source, after that about every 8- 10 months I would do the same water change schedule, 25% twicce a day for 3 days or so, with the water well prepared in advance.
If your using straight tap water, thats likely the source of your problems, good clean RO water can usually be found cheap, I buy 5 gallon buckets of RO premixed saltwater from my main LFS for $5 even, and 2gallon jug of RO fresh for top off makes maintaining my namo a sanp, water changes take 5 minutes tops, and 5 bucks a month is pretty darn reasonable.
