I had a service call on Friday to replace a light fixture that the customer thought was rusted and the source of the algae. His was green and I got the fixture out by brail. The ring was rough and oxidized, the housing had an orange coating of oxidation that wiped off mostly and the light cable was that typical cyan copper stain color. The light is an old Swimquip 5082, fresh water only (fresh water pool) fits niche 5068-12, 15 and 17. There is also the number 60000-658. The iron level is .1 which is in range. The copper is very high at .8-.9. The chlorine levels according to the customer won’t hold. Recent test TC .15 and TC is 1.1. Customer adds chlorine but nothing happens. Customer was told rust from light was causing high copper. I’m not sure how iron causes copper. In my last conversation , I asked the customer to have his tap water tested for copper from the source he uses to fill his pool to rule it out. My question is Is the light fixture causing the copper or is the copper causing the light fixture to oxidize and discolor. Is the algae caused by the copper or is the difference in FC and TC enough to cause chloramines? I’m thinking he has a few issues. He also has a sand filter which hasn’t had a sand change in 7 years. Thank you.