BBB method and vacation???

[waterbear]

Besides the borates I wonder if algae growth is constrained by other factors that relate to the pool's environment.

Your avatar betrays the use of a bird cage (enclosure) that are so ubiquitous in Florida. That would be one variable and must reduce UV exposure. Other possible factors: cloudy weather and summer rain (there's almost none in the southwest and large portions of California during July and August); humidity; day/night air temperature swings; cover usage; etc.

Nope, pools turn green here in a day, birdcage or not! Summer rains tend to bring on algae blooms also (probably by diluting the chlorine). I would have more customers coming in right before a rain to get some chlorine to shock as 'insurance' and even more come in a day after a heavy rain to get help with clearing their now cloudy and/or green pool.
Proper cover usage should not affect algae blooms since the covers should be on at night and off during the day but that is really a winter thing here and not a summer thing.

FWIW, borates ARE an effective algaestat (and pH buffer).

[CarlD]

Excuse me if I asked this before but early-onset Oldtimer's Disease is setting in!

How compatible is a high borate level with higher levels of PolyQuat? I like to give a solid dose of PQ early on in the season then add weekly doses. It doesn't kill algae but if my FC drops it gives me breathing room to boost it without fighting a bloom.

For those who are unaware, raising borates means adding LOTS of Borax and LOTS of muriatic acid to keep the Borox from sending pH through the roof.

Adding a quart of PolyQuat will make your FC appear to disappear after 48 hours so you need to boost THAT as well.

[chem geek]

I believe that the borates (which is mostly boric acid in water) and PolyQuat are compatible and do not interfere with each other. Both will inhibit, though not completely stop, algae growth. As you noted, chlorine will oxidize PolyQuat breaking it apart into smaller pieces so that creates a chlorine demand, but the smaller pieces are still effective at inhibiting algae (though they no longer act as much as a clarifier when broken up). Eventually, even the smaller pieces get oxidized, but that takes longer and is one reason why you need to add more PolyQuat weekly (in warmer water; in cooler water everything slows down).