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I know a lot more about water treatment than ponds. I concur with much of the advice here. Iron only becomes soluble at high concentrations in the absence of oxygen. So this water will be devoid of oxygen, and it will consume some oxygen when oxidizing. Iron itself is not very toxic, but low oxygen concentrations will kill your fish. And the oxidized iron may make your pond ugly. Iron in water without oxygen is dissolved and the water is usually clear, as soon as it oxidizes the red iron precipitate forms making iron colored water you see.
How to treat it depends on iron concentration and pH. Oxidizing almost always works, cascading through gravel filled buckets as Fishin Rod suggested will work. However 70 to 80 gpm that may take a lot of buckets, and if you have much iron it could clog the buckets quickly Might be worth a try. Could you build a stream to feed the pond, with some drop and riffles that could work. But the red oxidized iron might look ugly. Spraying the well water into the air could also work, but the oxidized iron will end up in your pond. Not toxic, however if you have a lot of it you might not like the way the pond looks.
I have used greensand filters, it works a bit like a water softener. At your flow rates and if your iron concentrations are high it could get expensive and troublesome to operate. If your concentrations are low it could be fine.
Some people put aerators into their wells to oxidize the iron before pumping, but that will clog your well and/or pump. I don't think its a great idea.
Best of luck with it!
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