I currently use a Gamma UV in-line. One of the considerations to make sure of when you purchase a UV - is dwell time - the time that the water passes through the sterilizer the longer the Dwell time the more UV that the water recieves. Depending what you read - UV's can be used for alage control and somewhat for pathogens. The higher the wattage and dwell time the better to help with water borne pathogens - again depending on various factors. That is why twists are used to increase dwell time. Wattage of course - and the other is to identify current output of the discharge tube (
GPH) that you will connect the UV to and match the gph of the uv to the output. For my 55gal i use at least 18w (gamma) and 450-500gph on the output line - so at least a turnover 0f 8 times. The gamma does not have a built in wiper so i clean approx. every 3 months. Secondarily, some uv's on the market appear to be made in China but require the use of a an additional transformer for US
AC. To be safe, in my case, i use a name brand with history behind it, even though cost is higher.
Sorry to be long in the reply, and not to tell you anything you already know, hope this helps.