Yep I am very very familiar with that using ground water with about 2.5 mg/l iron for my previous trout pond and my indoor RAS tanks. Not sure if I posted this before, but here is how I get gin clear water in 24 hours for make up water for my recirculating aquaculture tanks. When refilling I use a garden hose nozzle to aerate the water. I just let it do it's thing overnight and I have gin clear water the next day. The more it's used the better it works as the iron particles attach themselves to the iron precipitate coating on the filter material.
Water gets pumped from one barrel to the other via 30 watt mag drive submersible pump and is pulled back through filter material via a gravity operated 'u-tube" siphon.
Why remove the iron? The iron can be stressful on the fish depending on the species and size of the fish as it is sharp edged and can irritate their gills. Trout are the most sensitive as are smaller fish with finer gill filaments.
In larger volumes of water at low flow rates it's not an issue as the iron precipitate gets diluted and settles. However in my 100,000 gallon trout pond at 45 gpm it still created a opague green color as it was settled and diluted somewhat but not completely.
