OP, I'm looking at a few acres of the same sight, supposedly good if <25% of pond is covered as pictured.
We have 'creeping fertility' and your grass carp have done what they can, or will. They favor some plants, ignore others. They can clean out a pond, going too far. They're not legal in most states, and triploided carp (neutered in hatchery) are preferred to prevent planted or escaped specimens from reproducing. What yours haven't eaten by now, they likely won't.
Many times, when people have a pond, they encourage waterfowl use; and this should be avoided as waterfowl add excessive nutrients when on the pond. Do not feed the fish in your pond artificially formulated diets, as these are rich in nutrients and promote aquatic plant growth. When ponds are constructed, keep deciduous trees away from the pond because when they lose their leaves, many end up in the pond as another source of nutrients to promote excessive plant growth.
Once excessive aquatic plant growth occurs in a pond, the pond owner has to make a decision on what control methods to take to correct the situation. Many think that the use of an aquatic herbicide is an easy approach to this problem. There are specific aquatic herbicides that are effective on certain aquatic plants and, for the most part, they are expensive. Some aquatic herbicides require that you hire a certified applicator to use a specific chemical. The use of aquatic herbicides is only a temporary approach, as they will kill the aquatic plant that will die and ultimately release its nutrients and start the growth cycle over again. When one aquatic plant is controlled, usually another one will take its place as the nutrients are in place to continue to drive this aquatic plant growth.
We need to increase oxygen levels to improve a balance within the ecosystem. Weeds consume oxygen at night, offsetting what they produce during daylight. Windmill aerators are given short shrift because many ponds are just too big for one or two. Like with many electric-powered systems 1-2 emitters per acre is commonly recommended. I plan to use just one windmill, and to rotate between several emitters on a daily basis over three+ ac. Like aquarium bubblers their purpose is misunderstood. They don't aerate as much as they
circulate water, allowing O2 to be absorbed at the surface which happens more slowly than the bubbles can rise.
Muskrats suck, eat cattail roots and leave 95% of each plant to rot/compost. When I can't set traps by canoe I stalk and shoot them from shore. Nothing will remove bait-fish cover more quickly, or leave more mess. I use Weed Gator to gather other wet green mat'l to inoculate/moisten compost, but while it's probably the best such device it will clear swimming areas, but not large ponds. (~25' reach from shore, brings in vs leaves floating what it rips loose.) What we kill in situ becomes a catalyst for more 'composting' of weeds if not removed.
Geese seem to be the worst accelerators of pond fertility, adding much to natural decomposition on the pond bottom. That process can poison fish with gasses trapped below the most solidly-frozen surfaces. Get the floating gator head with glowing eye and put it out in Spring & Fall. Yell and wave arms at those it doesn't scare off. :laughing:
Any boil that keeps a few dozen square feet of ice 'open' in Winter will do wonders to dissipate gas output from 'composting', esp compared to doing nothing. If used in shallow-enough circumstance, a septic-aerating pump may suffice as a cheap shortcut but IIRC 3-4" is a max depth. It takes a good deal of flow and pressure to get a productive boil, but that's our best remedy for larger ponds (>1/2ac). A fountain pump (got solar?) is another aerator whose visual effect masks it's functional purpose. (see retention ponds for high density housing, where fountains are doing what we want.)
