The dead fishes were found floating on the surface of Saravanapoikai tank of Sri Subramania Swamy temple, used by the devotees to perform holy rites and to take bath after tonsuring their heads.
There was no change in the colour of the water, though stench emanated from the tank. The fishes were found dead two days back.
"We suspect that water pollution due to excess use of detergent soaps for washing clothes could have caused the death," Executive Officer of the temple, Chelladurai said.
Local people suspect rivalry inbidding for harvesting of the fishes which could have led to poisoning of the tank.
Residents also suggested fencing the tank and preventing public from using detergents or toilet soaps.
The temple officials said the tank had been cleaned and the dead fishes have been removed.