After some experimentation and thought, I have just recently committed to a full production run of a slot pipe light blocker. It's been a long time coming, but I guarantee it will be worth it. My initial trial runs were made with vinyl film and flex PVC "clips". I have gone as long as 3 weeks without cleaning my scrubber and have had zero growth into the slot - I don't even have to scrub the slot with a toothbrush, except for maybe around the rotatable ring. Unfortunately, this was not a user-friendly solution. So, I developed a concept for a one-piece snap-on light blocker, and had a prototype knocked out on a 3D printer for $5 This is a 3" section, which fits over one half of an L2 slot pipe 2 of them fit the pipe perfectly As you can see from this cross-sectional view, the 'tabs' of the light blocker get close enough to the screen to block the light to the slot pipe junction, but they do not touch the screen and interfere with water flow. I found that this is very important, otherwise the flow can get 'pushed' to one end of the screen. The light blocker snaps on tight enough so that it won't slide around too easily, but it is loose enough such that any growth will allow it to rotate on the pipe and self-adjust. The light blocker is flat on the top so that you can get it level without having to take off the light fixture and try to eyeball it. This design also allows for the production of an injection molded slot pipe, but with the latest version of the slot pipe now finalized, it's simple enough that I don't really see that coming to fruition anytime soon as it is rather cost prohibitive. The extrusion template is in line to be manufactured, but it's probably a couple weeks out. The first production run should start shortly thereafter, waiting on a date for that. I expect to have product in hand by the end of the year, and as long as the extrusion work is satisfactory, I will start shipping these out to all my existing customers immediately.