Pool stores don't know what POLYQUAT is...

[chem geek]

Carl's "Poly..." suggestion is good, but if you wanted to know the actual full name (just to be sure) it is:

Poly{ oxyethylene (Dimethyliminio) Ethylene (Dimethyliminio) Ethylene Dichloride}

It is in the chemical family of Polymeric Quaternary Ammonium Compound, but it won't say that on the bottle (though it will sometimes say that on the Material Safety Data Sheet, if provided).

The reason I wanted to give you the full name is that there is another related substance used for algae treatment called Polydimethyldiallyammonium Chloride and this is not the same thing as PolyQuat though it is closely related.

Richard