FC/CYA/Temperature relationship?

Florida. I have learned that my pool needs FC to be about 10% of CYA in summer to keep algae away. (FC=7 when CYA=70). If FC drops to 5 for even a few days, the pool starts to get a green tinge which I can quickly control. But now its October and the pool is about 10 degrees cooler. (I haven't measured the temp.) When I used a tri-chlor in-line feeder I dialed it back around this time of year.

My question is, should I expect to need a lower FC/CYA ratio with colder water to keep algae away? (My gut tells me that this is so). Of course there's also less sun on the pool and less of a bather load (which is always light). If I were to install solar heat, and raise the temperature back to where they were this summer will the FC/CYA ratio I need go back up?

Your gut is right. Colder water inhibits algae growth. Here, up north, we expect when the water is below 60 deg there is very little algae growth, especially in a pool that was shocked just before closing. I frequently open in the spring to no algae at all.

Thanks Carl. I let my FC drop to 5.0 for the past few days with no hint of green, but it made me a little nervous.