Is there an easy way to control grass? I have many lilies, marginal and
oxygenator plants. There are frogs & tadpoles, snails and golden shiner
minnows also. The water quality is good and in general maintenance is
minimal except for pulling occasional weeds on the moss covered cement
walls and the grass on the clay bottom.

I have a clay bottom 18,000 gallon (17'x 47'x 2-4) lily pond which is
spring fed. It filled up in 2 days so the flow is good. The spring
water's temperature is 50 F. The pond's temperature is up to 65 F.

The grass is growing on the bottom and it grows about 3 foot tall.
Fortunately the shallow end has a cement bottom and no grass is growing.
But in the 3' to 4' deep section, there are some rather large bunches of
grass growing. The grass looks reddish-brown in the water but when I
pull it our it is green, not just a bright green. The blades are narrow
and very long. I have been pulling it out by wrapping it around the
blade of a pole saw and pulling it out. Some times I get roots,
sometimes I don't.