Do you have a reference that is making you so wary? I found the study thaf suggests further research on azolla but doesn’t seem conclusive enough that I’d stop feeding it.
https://www.academia.edu/10074317/Azolla_BMAA_and_Neurodegenerative_Diseases
I got some from an Etsy seller last fall. I’m trying to build up the amount I have but so far it’s not as prolific as azolla or the larger duckweed. One thing I figured out is that I have to keep the buckets covered with screen or else disturbance from rain water washes the wolfia onto the side...