How fast should Algae eat Chlorine?


Jun 1, 2016
Good afternoon,

Working on a SLAM right now and have needed to add Dichlor to bump my CYA up (will need to add more to get up to 30). I've been doing quite a bit of brushing and vacuuming, so much so that I'm bumping my DE filter every 30 minutes or so. I'll be pulling it apart, cleaning and adding fresh DE later today.

The pool is blue, but cloudy, and I've got algae that I keep vacuuming out from the floor. Why is my chlorine not dropping fast when I still have algae?

FC: 10
CYA: 20 (will be adding dichlor)
CH: 25
TA: 50
pH: 7.2

I guess I'm expecting my FC to be, like, 5 when I've still got 10 after 2 hours now.. in the sun with low CYA. What's confusing me more is that I had just brushed a bunch of green water through my normal test site before testing again and I still had 10 FC. Is this normal?


Mod Squad
TFP Expert
Apr 4, 2007
SW Indiana
When the pool is blue, you are dealing with mostly or all dead algae so the chlorine demand will be much lower than when dealing with live algae that is reproducing.
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