In our situation, I dont think it matters that much.
It takes a certain amount of 'exposure' to the UV light to kill one of these zombie bugs. You can increase the exposure three basic ways.
1) more power. More watts will kill faster at longer distances. Think lazer blaster vrs sun lamp.
2) More exposure time.
You can increase exposure time by pumping the water by the lamp at a slower pace = lower volume/hour - or - run the same water by the lamp more than once.
3) add more UV units in parallel or series. Both will increase exposure.
Im going with #2. My circulating pump in the rez is 390 GPH. Im going to set up the lamp so that it is in a relatively calm part of the rez - probably in the center, out of the direct blast from the pump. That will mean slower moving water right at the lamp for longer exposure. The water will cycle by the lamp multiple times each time the pump turns on. Right now Im running that pump one minute every 5 minutes, but I may extend that to something like 2 to 3 minutes ON every 10-15 minutes. Maybe.
I dont think we need the lamp on full time, plus I dont want to precipitate too much iron. That will also extend bulb life by not running full time.
If I add a stainless tube to protect the plastic, I will do the same - just direct a small portion of the total pump output through the tube.
Interesting idea! I may even have some SS ducting laying around.....
Exactly! I love these forums for that exact reason. Most of my best ideas come from other people