I have a pond with algae problems as well. It composts well and makes a decent mulch as wellI also came across this.... lol
https://algenair.com/blogs/news/the-benefits-of-algae-as-a-fertilizer
Now I'm thinking that I WANT the algae to grow.... We do have a big compost pile. Lots of animals (horses, goats, chickens, ducks, rabbit) that provide ample manure. I also use a lot of compost.... Since the cost of fertilizer is going lunar, I've been thinking of ways I can possibly fertilize my pasture with something natural. Beyond the garden as top priority, this looks like a potential method.... I can keep harvesting the algae, compost it, and spread it out on the pasture a section at a time.