My neighbor has the same problem.. first had a heck of a time getting rid of the "slime" cyano using Chemi-Clean, and after months of battling that to finally get it out of his tank all of the sudden a month later the "stringy" cyano appeared. Now he is battling that. He has a Mag18 return pump/dual returns, Koralia3 and Koralia4 on his 75G and still can't get rid of it. Also runs a phosban reactor. Definately frustrating to say the least. He was never known to take a proactive step to rid it though.. just waits until it is out of control and hindering his viewing pleasure before he decided to do something about it.. at that point it is a long hard battle. The only thing he is good about is doing a 20G a week waterchange and changes out his media (chemi-pure/rowas phosphate remover) monthly. That doesn't seem to help his problem though and in 5 years I have never seen him do a single test on his water so who knows what he is putting back into his tank with the water changes. I have even offered my test kits to him but he says they are "too much work". Definately frustrates me when he complains about stuff like that but won't put in the effort to even do a test to find out the source of the problem.