Three temple ponds with permanent blooms of blue green algae were highly productive . They all showed high alkalinity . hardness, electrical conductivity and pH . Organic carbon and nitrogen were highest in Sarvatheertham pond-6o to 79 .6 mg./1 . C and 4 .10 to 7 .6o mg . / I . N . In Tamaraikulam it was 16 .5 to 20 .3 mg . C/1 . and 1 .03 to 1 .32 mg. N/1 . In Sarvatheertham, the gross production ranged from 2 .85 to 20 .72 g . O2/m .2/d . Self shading by blanket algae of blue greens reduced productivity in Sarvatheertham, where a persistent thermal and biochemical stratification was noted . Very high organic carbon and nitrogen contents were noted in Sarvatheertham pond . The dry weight of plankton in this pond ranged from 430 to 90o mg ./1 . Productivity computed from diurnal changes in alkalinity and dissolved oxygen also revealed a high rate in Ayyankulam, Tamaraikulam and Sarvatheertham in descending order . Very wide fluctuations in pH, both diurnally and depth-wise, were recorded in Sarvatheertham and to a lesser extent in the other two ponds . Photosynthetic efficiency was 4 .03% in Ayyankulam, 2 .09% in Tamaraikulam and 1 .56% in Sarvatheertham . By the diurnal oxygen curve method, a gross primary production of 97 .5 g . 02/m2/d was recorded in Ayyankulam .