I spent a pleasant career in fish farming, and usually, at least in the northern temperate climates, potassium is the limiting factor for algae growth in ponds, algae is the basis of the food chain for the rest of the pond environment. In tropical climates, the first limiting factor is usually nitrogen. So when I was working in the Niger Delta with the mangrove tidal ponds, we'd dump a sack of urea into the ponds on a weekly basis. Turned the pond bright green in a matter of hours. It was hot, too, which helped. Those were big ponds. There was a urea factory within 50 miles and it was subsidized. They use natural gas to make urea, and in Nigera, they flare the stuff off, they have so much. Elsewhere, we used manure from chickens or ducks or pigs or all three. That mammalian / avian classic combo that is the basic incubator of all things nasty and viral. But I didn't know that then-:-)>.
