I had one in my old freshwater tank. It was good at eliminating algae blooms.
	So I believe that they can eliminate free-floating algae quite well.
	Unfortunately, that cures a symptom, and essentially hides an underlying nutrient problem.
	
	With my recent ich outbreak, I researched them a bit for disease control.
	They appear quite useless against that, although might work against a few other pathogens.
	Just not intense enough.
	
	So I guess it depends on what your planned purpose is.