Tilapia,carp or koi. Adding a few of these fish to your pond can be all it takes to maintain a healthy balance with Duck weed, they eat the weed, you eat the fish.
Some years ago I read of a man who put some expanded metal "tables" that were above the surface of his pond, he would put the remains of the fish he cleaned on them, the maggots from them would fall into the water and the fish would eat them (he claimed).
I'm wanting to do something like this some day when I get some land. I'd like to have a few talapia pools, not in sunlight so they don't build algae that much. Maybe put a chicken coop elevated above the pools to feed the fish.
You may want to consider some apple snails and carp for algea control. That may remove the need for a filter. Do you have a solar or wind powered plan for aeration? If not, maybe consider catfish who can come up for a breath on their own. Overall, cool idea. Please keep the updates coming.