So we did manage to experiment with this, but certainly need lots of improvements. Here's what I found over the last 5 months. Unhappily, the resulting pond is NOT esthetically pleasing, but functional.
We had a 20 gallon rubber pan we filled with water every day and drained, but ducks being ducks, it was mostly mud most of the day. Funny, though how the chickens and guineas also prefer the duck-flavored water over the fresh clean drinkers, no accounting for fowl.
I bought a 500 gallon kiddie pool, the type that have rigid sides and a soft rubber bottom for $18. Its about 18" tall and about 8' in diameter, and I dug a hole to put it in so the top edge was an inch or so higher than the ground. I also tried to make the center deeper than the sides by a few inches, not too much though because I wasn't sure how much stretch the pool would tolerate. we surrounded the pool with large rocks to keep the duckies from taking mouthfuls of dirt to rinse in the water, and also surrounded the whole area with a thick layer of mulched shredded bark.
Then we got one of those 150 gallon stock tanks, and made a version of a 'skippy filter' - put a plastic frame we had lying around that divided the tank in half. I didn't buy floor scrubbers, but instead used a roll of the blue swamp cooler pads, I meant to chop it up, but my husband was in a hurry (we were leaving town the next day) and we ended up just laying three layers flat. This left more room for us to stick plants in the top, but I don't know if it might have been better to have more gaps in between.
Then we took a 5 gallon bucket, cut slots out of the sides, and put in a $40 pond pump that pumps 600 gallons per hour, At first I surrounded the bucket with more of the swamp cooler pad stuff to filter out leaves and feathers but it fell apart quickly, later used some netting which was too fine and clogged too quickly, and how am using window screening which I rinse off once a week - seems to work best.
I trudged down to a dry stream bed that cuts through our property and dug up some cattails, and put them bare rooted in 2 gallon pots with stones to weigh them down. the pots didn't really stay in place, so I put some field fencing over the top of the tub and threaded them through. they filled up the center third of the tub. Then I bought a red, white and black mangrove seedings - but they don't like our climate here, I think only three of the 50 plants survived, I'm keeping those in the greenhouse to see if I can get them better established and will have to bring them in most of the year - even in summer it gets down to the 50s at night at my house, which may be too cold for them. However it could be 95 during the day (I'm at 7000 feet in the NM mountains) The plant I had great success with was water lettuce - I ordered some on
amazon and got 5 little plants in a zip lock in the mail. In a few weeks, they had choked out the tub, so I'm hoping they are cleaning as much as it seems! I also ordered duckweed, since its a good food for them, I hear 40% protein, but I couldn't get that established. I may try again in the greenhouse.
So in a way, we have a working system. I have 11 ducks which is very hard on this little pond, and the water does get pretty icky. Every two weeks or so we pump out 3/4 of the water into the garden and orchards. But I worry the water is getting septic sometimes, especially now in the fall when the algae doesn't grow (I think it was doing a lot of the cleaning too) It is not a pretty pond, but the ducks love it and the chickens and guineas venture out into the rocks we have in the pond to get a drink too,
I think next spring we'll add another filter with sand and gravel. Also, I wish I had a slope to the pond so that solids (feathers, leaves and poo sludge) could be more easily removed. I've never cleaned my 'skippy filter' but I have pumped out all the water from it, leaving the sludge thinking all the good bacteria is in there, but I still think the system is overwhelmed by poo. I'd like to also do more hydroponics - maybe pump the water through shallower trays where we can grow stuff for the flock to eat or even veggies for us.
A few times we had power failures and all the water in the filter tub siphoned back into the pond, sometimes flooding the chicken yard. My husband came up with a brilliant idea - he put a connection on the hose from the pump to the filter just over the filter's edge that we can tighten when we want to siphon out the tub, but we keep it loose most of the time. It drips a little into the tub, but that's OK, if the pump stops it isn't air locked and the suction is broken so the water stays where it should. Way cheaper than buying an air lock!
So, its not exactly sustainable yet, we still need to exchange the water at least once a month if not sooner, but we've been able to use rain water from collection tanks instead of our scarce well water, and we don't need to scrub the muddy/poopy pan every day which is a huge time saver. It doesn't use less water, but we can recycle the water more efficiently for the garden.
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I'm not sure what our plan is for winter - I don't think we can keep it from freezing We've though of covering it with a mini greenhouse hoping that the water might hold some heat from the sun, I'll post updates as we make them.