Consider one or a few floating islands to absorb nutrients. Islands in Fall can be pulled to shore and surface vegetation removed to get sequestered nutrients out of the pond ecosystem. Use google to search for floating islands both commercial and homemade. Quite a bit of research has been performed using floating islands to sequester nutrients in ponds and lakes. Some threads are here on PBoss forum about floating islands.

https://www.pondboss.com/news/inside-pond-boss/floating-islands-clearer-water-and-more-fish

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=500899