Building a Large Water Garden with Well Water: Filtration and Water Softening

Well Water Challenges

Hard, iron-rich well water stains and can harm fish. A water softener exchanges calcium/magnesium for sodium—generally safe for pond fish at typical levels. Test sodium; if very high, blend with untreated water.

Iron Removal

Use an iron filter (greensand or aeration/settling tank) before the pond. Or let water cascade over rocks to oxidize iron, then settle in a pre-pond basin.

Filtration for 4000 Gallons

A large biofilter (multiple totes or a dedicated bead filter) with a properly sized pump is essential. Avoid undergravel or simple sponge filters—they'll clog.

Biological Filter Design

Search "DIY biological filter" for plans. A multi-chamber system with brushes, matting, and lava rock handles high loads.