Check out pictures on instant holding areas for Azolla, using inverted mosquito nets.
You don't need a deep fishpond to multiply Azolla. Shallow ponds are doable and cheap for this project. Line them with thick pond liners, or used billboard tarpaulins. Prepare the pond with your IMO and beddings.
We can't have too much of Azolla as it may be fed to animals, used as green manure, and shared with others :)