+ 1 to soulsigma's reply is pretty much spot on.

Cyno is a straight up Nutrient rich condition in your tank. Anything you do that does not adress the root cause is a waste of time and effort. It might go away for a few days but it will be back!

The anti-biotic thing does work. But thats the problem it works too good, cuase it kills off the good bacteria as well as the bad bacteria. Not a good thing to be doing in a reef tank, especially in a tank with a pretty good bio-load already. But if thats the route you wanna go it will work.

While increasing the Clean up Crew has some solid merit to it, no go on the Sand Sifting Starfish. It will quickly deplete the home aquariums sand bed of sand bed fuana and then slowly starve to death, die and rot and contribute to the problem in the end.

Again this is just my opinion and thoughts on this subject, so take it for what it is...