dont use dyes if you are interested in fish production. pond dye will not control duckweed. Diquat (label name Reward) is excellent on all the weeds you mentioned. If you start early and appy 1-2 gallons per surface acre when weeds begin to grow. diquat offers the most bang for your buck. its a contact herbicide so the weeds have to be present and growing for it to work.

I'm a professional applicator in Georgia and use diquat often. BE SURE TO READ THE LABEL and wear gloves and a face shield. I once got some vapor in my nose while spraying on a windy day. the diquat will eat up the soft lining of your nose bad. I had nose bleeds for 2 weeks.

SHAN