Looks to me you grow it large scale.
Why horse manure? Cheaper? More available? Curious mind?
You can't give horse manure away here. Heck, you can't even pay folks to haul it away here. It is largely regarded as one of the worse fertilizers around.
One would thing you'd just have fish in your tanks and call it good. With outdoor tanks like that, you wouldn't even have to feed the fish. I know Azolla is suppose to keep the mosquito population down, but nature finds a way.
My favorite fertilizer is rabbit poop. I have friends who operate rabbit rescue missions and I get all the free rabbit poop a girl could hope for. (No, not really, I could use twice as much, but I make do.)
I don't have enough Azolla to use it as mulch, wish I did. I do have a healthy supply of other floating water plants that I fish out and dump on the garden as needed.
