I haven't tried adding more than 1 gallon/week. In theory, CS would likely kill the algea, but it probably wouldn't do much for things like body oil and general other pollutants. For that you will definitley need something else. If you are strictly oppossed to chlorine, then a powder oxidizer would be the most ecenomical. 35% H2O2 (Hydrogen-Peroxid) would be great, but it could be cost prohibitive. The best I can do locally is technical grade for about $12/gallon and depending on the pool size, you'd probably need several gallons/week.