Orange-Brown Pond Water: Solving Tannin & Sediment Issues

1,200-gal pond, dark orange-brown water, fish healthy. High pH (8.5–9), 300 ppm alkalinity, softened water (iron-rich). UV, biofilter, daily pre-filter cleaning. Algaecide used. Carbon didn’t help.

Root Cause: Iron & Tannins

• Softened water exchanges Ca/Mg for Na—**does not remove iron**.
• Iron oxidizes to rust (orange-brown) and stains everything.
• Tannins from leaves/mulch add tea color.
• High alkalinity buffers pH up—limits plant nutrient uptake.

3-Step Fix

1. Source Control: Test fill water for iron. If high, use an iron filter (greensand/air injection) on fill line. Check liner for leaks introducing soil.
2. Water Changes: 20% weekly with *untreated* (non-softened) water if possible, or RO/DI blend. Dilutes iron/tannins.
3. Polishing: Add polyester filter floss in canister to catch fine particulates. Replace weekly.

What to Stop

• Algaecides (copper-based) — accumulate, harm invertebrates.
• Water softener bypass for pond fill.

Clarity will return as iron load drops. Plants (lilies, hyacinth) will help once pH stabilizes lower.