My auto chlorinator slowed down on me, so I started to get some algae on fittings. I slammed and all is well. One "odd" thing I noticed while holding FC at 18, is when my sample turned clear, it would keep turning pink after a few seconds. Add a drop, and is clear for a few, then oozes to pink again. Normally once it turns clear it stays there. Could it be the powder keeps dissolving in cold water? Pool is at 45 degrees, but I would think sample would warm up fairly quickly. Anyway, waiting for FC to get back down to 5 (it's still at 16 after 2 days)... cold water and clouds makes for real slow chlorine degradation!