+1 on siphoning some out but it will come back
+1 on adjusting a power head if you can.
I'm still working on getting some chemi pure elite to try. I have some cyano
too. It wasn't bad, but one morning I was like holy cow! So I siphoned out all I could see. There's a little here and there now, but nothing too bad. If it starts getting crazy again I will siphon again.
Here's a question that may help you also. I have purigen in my freshwater tank. If I recharge it like they say could I then use it in my saltwater tank? Cause purigen helps remove nutrients and nitrates. I'm thinking I may have a phosphate issue though since my trates are ~5ppm. I believe Hank is running purigen in his 55.