The paper describes the physico-chemical characteristics of water, diversity and periodicity of phytoplankton.  Surface water samples were collected at an interval of 30 days for a period of one year using plastic cans of three litre capacity.   Standard procedures were followed during collection, preservation and analysis of water samples for various physico-chemical and biological parameters.   The physico-chemical parameters studied were within   the permissible limits.   The phytoplanktonic community is represented   by five classes and seventy two species.   Density of the different groups of phytoplankton is more in the summer season than during rainy and winter seasons.   Based on the results of Nygaard's and Palmer's algal indices it has been deduced that, the tank is eutrophic.   It is high time   to formulate some   strategies for the conservation of the tank and to restore the   water quality.

Department of PG Studies and Research in Environmental Science,
Kuvempu University,
Jnanasahyadri – 577451,
Shimoga, Karnataka, India.

* Karnataka State Pollution Control Board,
Bangalore. Karnataka, India.