Influence of stabilizer concentration on effectiveness of chlorine as an algicide.

Cyanuric acid, used as chlorine stabilizer in swimming pool waters, has a relatively minor effect on the algicidal efficiency of free chlorine. The toxicity of free chlorine to three swimming pool algae was reduced slightly by 25 mg of cyanuric acid per liter if inhibiting, but less than algicidal, concentrations of chlorine were employed. Higher stabilizer concentrations (50, 100, and 200 mg/liter) generally resulted in no further reduction in the algicidal efficiency of free chlorine beyond that observed at 25 mg/liter.

Laboratory comparison of the effectiveness of several algicides on isolated swimming pool algae.

The most frequently encountered species of algae found in swimming pools in the Phoenix metropolitan area were used to evaluate the laboratory effectiveness of five commercially available pool chemicals used for algal control. The pool algae used were the xanthophyte Pleurochloris pyrenoidosa, the chlorophyte Oocystis sp., and the cyanophytes Phormidium minnesotense and Plectonema sp. Pad Algae Kill (a chlorine derivative) was effective in the control of all test organisms. Algaedyn, a silver-containing algicide, was effective on P. minnesotense and Plectonema sp., but caused only a slight inhibition in the growth of P. pyrenoidosa and Oocystis sp. Quarternary ammonium (Padicide) was more effective in controlling the growth of Phormidium and Plectonema than Pleurochloris and Oocystis. Algimycin (herbicide) only reduced the growth of Oocystis and was ineffective on the other species. Bio-Gard (copper) reduced the growth of Pleurochloris, but had no effect on the other test organisms. The technique used to quantify the influence of algicides on isolated pool algae appears to be adaptable to those algae that form distinct colonies on an agar substratum.