Generally Cyano = Phosphates are too high.
I have been having an ongoing fight with Cyano since transferring to the 100g (as I have had constant phosphate issues).
Best course of action is to remove the phosphates and then it will go away:
* Use a good brand phosphate remover and replace often. Ideally in a phosphate reactor if using GFO based remover I use rowaphos and have recently changed it
* Use macro algae or an algae scrubber to reduce phosphates/nitrates. whats this? how does it work
* Decrease feeding amounts (if possible). Make sure frozen food is thoroughly washed and defrosted before putting it in the tank. I use new era flake, I think I was over doing it with three times a day so will cut back to once a day
* Make sure you are using a good source of RO water for water changes and top ups (RO water with as close to zero TDS as you can get). Im thinking of getting my own ro unit, the ro water I buy has a TDS of 20? is that too high
* Make sure you do regular water changes. Every weekend I do 20% religiously
* Make sure you have a good amount of water flow in the tank. Cyano cant grow as fast in high flow areas and higher flow rates will stop debris building up which rots down and causes phosphates (though you need mechanical filtration to remove crud from the water column). is this carbon? If so I have that and change it every month
I'm planning to start using liquid phosphate remover to knock my phosphate levels down. Its apparently good stuff but has to be used extremely carefully.
If you have higher nitrates as well vodka dosing can help too. However this has its dangers too so read up on it a LOT before you decide to go this route.