Koi Hanging in Shallows: Oxygen or Stress?

One koi stays in shallow water, back exposed. Swims away normally when touched. Water tests OK. Is it sick?

Likely Cause: Low Dissolved Oxygen (DO)

• Warm water holds less O₂.
• Shallows = more turbulence/gas exchange = higher DO.
• Organic muck (leaves, dead algae) consumes O₂ at night via decomposition.

Quick Fixes

1. Remove decaying organics (net, vacuum).
2. Redirect return flow to break surface aggressively.
3. Add shade plants (lilies, hyacinth) — cooler water = more O₂.
4. Run air pump + diffuser 24/7.

Watch For

• Prolonged surface gasping = emergency.
• Ulcers, swelling, clamped fins = disease/parasites.
• Ammonia spike (test at dawn).

Since it flees when touched, it’s not moribund. Fix oxygen first; reassess in 24 hrs.