Quote Originally Posted by PoolDoc View Post
If you remove nearly all phosphates, algae has a hard time growing.
If you maintain 50+ ppm borates, algae has a harder time growing, though I doubt the effect is as great as with PO4<100 ppb
If you maintain constant chlorination at FC=10% of CYA, as far as we know, algae will not get started, though once established, some algae colonies will persist.
Great info.

While I haven't maintained chlorine at 10% of CYA (I maintain FC 4-5 at 60-80 CYA), I do try to keep borates at 50ppm and add a phosphate remover when closing the pool for the season to keep phosphates down. Since starting this practice many seasons ago I've not had any algae outbreaks. Someone mentioned the phosphate treatment at closing probably wasn't necessary, but I think I'll stick with it since this routine seems to work well for my pool.

Perhaps the combination of low phosphates and the addition of borates is a double wammy for algae. Although I've not tried it yet, I'm thinking I might be able to discontinue the weekly polyquat (60%) doses. Perhaps I'll try that next season since I already have my supply of polyquat for this season.

Also, if the bucket test for metals comes back negative (I'll know tonight), perhaps I can also stop, or greatly reduce, the addition of the sequestrant (Jack's Magic Purple Stuff).

Thanks again for taking the time to help us.