I bought a 9W in tank one for 39$ at a local pet retail storem. Hooked it up, with a frysaver on my filter inlet, and let it run for a week. It was funny to watch, the outlet of the sterlizer wad a white cloud of nuked algae.
Cleaned the prefilter daily of the "algae dust" and I was set, no more outbreaks. I have not had to use it again, but it came about when I changed my substrate from clown puke to Turface.