I have an approx 5 acre pond with an earthen damn which flows into a creek then into the river. The pond is approx 25 years old and is only about 4 ft at its deepest point. In the summer it is choked with grasses of varying types. I have added 24 grass carp but not even they can keep up with the growing grasses. I assume this is a depth issue and if the pond was deeper, the grass would not get as much light and be reduced. I am afraid that each year that goes by the dying grasses will only work to make the pond shallower and perpetuate the cycle. I have tried an easy fix of a sandbag wall around the spillway to raise the level but am afraid of water pressure on the earthen dam causing a break.

What is the best fix? Drain the pond and dig it out?? Herbicide the grass?? raise the damn?? Other suggestions or combinations of the above?