Jc...
UV is what was previously mentioned...ultra-violet lighting, natures best sterilizer.
When looking into a UV, a few things need to be considered. The light will destroy all bacteria, most single cell algea, and most parasites. Each item above requires a certain amount of exposure to destroy it...bacteria is the easiest, parasites the toughest. The amount of exposure to the UV radiation is called dwell time. The dwell time and flow rate are the key factors in the destruction of the above 3. A smaller UV light, usually will require a less flow rate to perform as intended. The draw back to a smaller light is the inability to adequately perform for larger tanks. A flow rate of 100gph for a 90 gallon tank isnt that great. The same flow for a 29 or 45 is somewhat adequate.
As for the particular brand...that is a personal choice. Each manufacturer will have their own special gimmick as with all products. As an example...the double helix makes claim to using high tech polymer in their tubing which resists algea build up...algea is killed by the UV so how could it build up to begin with? This is only an example, not a choice preference.
Personally, the bigger the better in the UV lights.