Laguna brand is a well known as is Lifegard. Turbotwist by Coralife is a good unit but a bit pricy.
My 210 is utilizing a Laguna 1000 UV for a pond aplication. It is rated at 1000g and 500gph. I have been running this uv at 300gph for years and I have never had algea or disease. The unit uses an 8w bulb and the whole unit uses 11w total, very efficient. In order to kill pathogenic organisms, a slower flow rate is desireable over massive power...IMO. I like to save power. Just make sure the flow is at least the tank volume per hour and you will be fine.