Gorgeous jaw fish! Really vivid yellow heads!
http://www.liveaquaria.com/product/prod_display.cfm?c=15+1634+115&pcatid=115
I am considering 20 of these in my 150G mixed reef with decorative macro.
Maybe let the macros over grow to out compete the hair and cyano. Feed a little less to your fish. Manually remove what you can, and get some snails quick. Don't let your macros get coated. Tiny snails are best for that. Oh, and water changes!
Sorry for the unsolicited advice. I just can't help myself!
how deep is your substrate for the jawfish?
I'd be very interested how well this works. I suspect that you are thinking it will be similar to a clown harem tank? I had a 120 FOWLR that had 3 in it and that didn't work. One of the three ended up getting taken out by the others.
Don't you just love it when doing nothing is the best coarse of action? Salt water ghost shrimp ate all my ulva back in the day. Pods love it too.