I believe I would add about 30 grass carp. Koi and tilapia won't do it on chara.

Koi are scenic but aren't much good for weed eradication.

Tilapia are supposed to do everything but get out on the bank and mow the lawn. They seldom do much to stemmed plants. I believe it takes a lot more tilapia than people usually stock to even feed bass. Of course, that depends on how many bass you have.

Don't add the carp until the water cools down.