I'm impressed! You're definitely a head of the eight ball as far as the average pond owner and you are doing everything you can which is good.

How about seining the shoreline? Can you get someone in with an electroshocker boat?

You are aware the grass carp rarely eat the "moss" or algae right? But they are good for control of macrophytes. Talapia are good algae eaters though.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.