You can cautiously use the linear quat algaecides we usually dis-recommend. The same characteristics that cause the water to be foamy, also make it harder for those bubble breathing bugs to function. Sams' Club has a 2 gallon pack of that stuff for pretty cheap. If you get some, add the recommended dose, and see what happens. Just be careful -- that stuff uses up chlorine and makes the water more irritating. If you get a K2006, and post readings, I can help you 'tune up' to run the quats intermittently without having too much conflict with chlorine.