I live in North Texas and I didn't keep up with chlorine levels over the winter. (Do most people do this in my area?) After the ice went out of the pool this spring I went through the SLAM process and water returned that nice sparkling crystal clear look. After about 5 days, I had algae growing on the walls again. Restarted the SLAM and decided to pull the light out of the niche. This is what I found, courtesy of the GoPro. Just wanted to share my experience give folks an idea what might be behind your lights. 
