Polyquat 60
Also called: PolyQuat 60, Algaecide 60, polyquat.
Polyquat 60 is a quat-based algaecide sold at 60% strength, the most effective of the quat algaecides and the gentlest in a chlorinated pool. Polyquat 60 is the one algaecide Trouble Free Pool suggests keeping, and its real use is winterizing a closed pool, not a weekly dose.
Why it matters
Algaecide isn't a routine chemical: free chlorine held at the right level for your CYA prevents algae on its own. Polyquat's job is as a preventative while a closed pool sits for months, and as cover against algae while chlorine is out during an ascorbic acid stain treatment. It is not the tool for clearing an active mustard bloom, and it won't dissolve an established black algae colony. Dose the startup (maximum) dose printed on the bottle in your hand: products sold under this name state startup doses from 4 oz to 16 oz per 10,000 gallons. Avoid copper algaecides entirely.
In numbers
Check the strength before you buy. One of the best-selling algaecides in the category is 6% polyquat, not 60%, and its own back label calls for 97 to 128 oz per 10,000 gallons.