Greg's right, Reward is a better value just because of the % active ingrediant. Weedtrine D is weak 8 1/2 vs. ov 37% Reward. You just want the Diquat, water is a filler you get from your tap. Monsanto and Roundup just torch people on that scam. If you use Weedtrine D you might want to go 4 oz. and 1/2 oz surfactant. Get about the same % active ingrediant and stickum. The reason I'd go light concentrate first spray is I would try to hit the stacked or thicker areas first. That's can't miss. There is going to be stuff under the surface you are just not going to get unless you saturate. Plus, you can tell if the lower concentrate will work for your application. I am fairly certain it will, but with watermeal, you never know. You can always double or triple up next go round. Just the Weedtrine, not the surfactant.
I am not concerned about $, it's not that much, but usually my first application is per manufacturer's guidelines so I don't go way out there saturating a body of water with too much Diquat in this case. If you can bunch up spraying and don't want to wait a couple of weeks between applications I'd blend in a Cutrine Plus or Scythe. Then you can go hit it again in less than 1 week. Without going with Fluridone you will be spraying quite a bit anyway. But may save your desired vegetation. In my experieince I would really just Fluridone the entire deal and replant whatever plants I wanted back. Just for watermeal, no matter what the cost. How much is your time worth? There is a good chance you could be spraying 6 times or more, and even a slighter chance the Diquat is not all that effective. Make sure you use stickum. Where Greg and I disagree is concentrate % of active ingrediant. .5 % vs 3%. If I wanted better coverage of death I would just spray more of light concentrate. Especially when I am not under the gun with time constraints and know most certainly I will be respraying.
