BMAA is the neurotoxin (implicated in Alzheimers and Parkinsons). It also bioaccumulates over time, and potentially up trophic levels. So definitely not fish wonder food until there's some serious testing done.

Thank you. I will definitely look into this. At the very least, it still makes an effective and fairly high nitrogen organic fertilizer, while drawing down atmospheric CO2. It's so effective at harvesting CO2, ancient azolla sequestered sufficient CO2 (from 3500 ppm down to 650 ppm) to create a global ice age: https://en.wikipedia.org/wiki/Azolla_event

Edit: researchers are still studying the issue, but it seems some plants may be capable of concentrating BMAA, which is highly water soluble. Wheat seems to capture it in proteins of the shoots. I haven't found any further specifics other than cycads, which have a cyanobacteria symbiosis and concentrate it in their seed coatings.

Good to know about the possible neurotoxin. Any suggestions for further information on the topic?

Wikipedia?

Been there, done that and have read dozens of research papers on azolla as livestock feed, but there hadn't been any human research when I delved into the subject. That was quite a few years ago, however. I'll dig back into the stacks and see what I find. My chickens prefer azolla over just about anything, I need to grow more of it.