Conditions Which Determine the Efficiency of Ammonium Sulphate in the Control of Prymnesium parvum in Fish Breeding Ponds

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Abstract
Lytic activity of ammonium sulphate on Prymnesium was found to vary with temp., being higher at elevated temps. The decreased effectiveness of ammonium sulphate in fish ponds during the winter may be due to this fact. Lytic activity of ammonium sulphate on Prymnesium is greater at higher pH. The close correlation between pH dependence of the lytic activity and increased concn. of free ammonia at high pH values, due to dissociation of the ammonium sulphate, suggests that free ammonia is the active lytic agent. The pH of fish ponds was found to vary rhythmically during the course of day, the degree of variation differing in different regions. This provides a plausible explanation for regional localization of relative inactivity of ammonium sulfate. The efficiency of ammonium sulphate can be improved by adding it to ponds during the daily pH rise. Supplementing application of ammonium sulphate with unslaked lime further increases pH and enhances the lytic effect on Prymnesium parvum.

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