Probably Erythromycin - I just treated someone elses freshwater tank that had a bad outbreak of Blue/green, and it has worked wonders - gone in a day and no measurable effect on the biofilter at all. I'm just wondering if it might have a similar use in saltwater, although maybe there is collateral damage? Can't find anything that says DON'T use it, so maybe it hasn't been tried. Firstly we could just hook some out of a tank and see if the Erythromycin kills it, and if it does we can try it on a tank with cheap corals perhaps?