I think the best thing you can do is contact a local well driller for advise. You might not get ground water at 20', the water table might be much deeper than that. And they could advise you about what kind of well screen you'd need to keep the pump flowing all of the time. You also need to come up with a way to protect children and animals from falling down into that 20' deep shaft.

Fish naturally carry parasites.. and can live with that.. when fish experience stress their resistance to the parasites is weakened and this can affect their health and well-being... and yes, the parasite can cause death, too. If your pond went through a murky period, this can cause a drop in sufficient oxygen, which can stress the fish. Shutting off the pump may have caused even more stress and the water was not being arearated like it should. With cooler temperatures the water's bacteria level may not be high enough to breakdown ammonia buildup and debris that has accummulated in the pond. You have a deciduious tree, I assume with this comes leaf drop in the fall, these leaves will breakdown, settle in the bottom of the pond, and as they breakdown, plus the fish waste, can all result in an increase in ammonia levels, which is also a problem for the fish.. stress and low levels of oxygen. Since I am not a resident fish doctor, I can't say for certain what might have caused the death of your fish.. just wanted to share some info about fish health and stress, etc. Thanks.

UKYankee... Hi, and welcome to the forum! I rebuilt my pond last year, so its less than a year old now. It's roughly the same size as yours. Blanket weed is a big problem right now... previously I used barley straw with great success, but this year it seems to have no effect. Or perhaps the blanket weed would be even worse without it. I'm not too worried though - I suspect that my pond has not achieved a natural balance yet. Probably too many nutrients from the soil with all the new plants I added. It will probably take another couple of years before it settles down properly. I'm currently pulling out great swathes of it by hand regularly, but once the tadpoles start hatching I'll probably just leave it. As for green water, you can try a UV unit, but personally I have had no success with that method. I just got a thick suspension of dead algae instead of a thick suspension of live algae. Maybe I didn't get the right size of filter or UV unit, or the flow rate from my pump was too high or too low. Whatever, it had no effect on water clarity and just increased my electricity bill. So, when I rebuilt my pond, I went with a big DIY filter instead, based on the Skippy filter. Do a web search and you'll find Skippy's site whch has details. It's a "natural" solution, which may suit your philosophy. Takes a lot of space though (compared to commercial filters). Other things to counter green water is to have plenty of plants, especially a) a good coverage of floating ones (or ones with sperading leaves/pads), which will provide shade and therefore reduce algae growth and b) ones which grow rapidly and use up nutrients fast eg. watercress. Again these are "natural" solutions. I buy bunches of organic watercress from the supermarket, and throw it in the open top of my filter where it grows like mad. I buy lots of floating Water Lettuce and Water Hyacinth each year (they die in Winter), and the lily pads help as well. I have water soldiers too. I've had duckweed in the past which worked great, but was so rampant that I had to scoop out a bucket load almost daily. My current fish love to eat duckweed though, so that doesn't work any more (same result with azolla :-P) So far, floating plants and the new filter have kept the water clear, but the real test is yet to come this Spring and Summer when the temperatures rise and we get more sunlight. Well, whatever you do, good luck!

Thanks so much! The archives here have been more helpful than the whole rest of the internet honestly. The 25% or so photos that remain after the great Houzz coup are all really lovely and helpful as well. Yes, that's the "plastic ball in a box" filter for the pump that came with the house in 2012. So all things considered it's held up well! It's in almost total shade so we've never had any problems with algae, just being too lazy to skim out the leaves. It really had become its own little ecosystem by the time it finally started leaking for real, so I figure we'll give the new one a chance to do the same. I'm very eager to get some actual plants in and around there again. And we miss our toads! There are visible holes in the old lining, which is also very definitely not 45mil EPDM. The pavers are all just plunked down at random and slide in all the time, and there is visible slippage (please note the angle of poor St. Francis there; that "cascade" underneath him used to be flush with the rest of the rim of the pond). That's actually my only worry, especially being literally below sea level, is what it looks like under there and whether we'll need to worry about the structural integrity of the hole/rim itself. But we'll find out! Liner arrives today, 100lbs. Sorry, UPS guy. And I learned, probably on here, that doubling up on gloves is not at all overkill when dealing with the foam! Again many many thanks for the reassurance that at least in theory we're doing it right! I hope to have pretty pictures to share soon.