Koi Pond pH Management: Safe Adjustment & Stabilization

Target Range: 6.8–8.0

Koi tolerate this wide range. Stability > perfection. Daily swings >0.5 units are dangerous.

Adjusting Safely

• High pH (>8.5): "pH Down" (phosphoric/sulfuric acid blends) — dose per label, retest 1 hr later. Max 0.2 drop per treatment.
• Low pH (<6.8): "pH Up" (sodium bicarbonate/carbonate) or crushed coral in filter bag.
• Never use muriatic acid, vinegar, baking soda directly — unpredictable, dangerous.

Buffering for Stability

KH (carbonate hardness) buffers pH. Target KH 100–200 ppm (6–11 dKH).

• Test KH (liquid kit).
• Low KH → add Seachem Alkaline Buffer or crushed coral (slow).
• High KH + high pH → partial water changes with RO/DI water.

Common pH Drivers

• Concrete/lime leaching → high pH.
• Heavy plant respiration (night) → CO₂ → low pH.
• Rain (acidic) → drops pH in soft water.
• Algae bloom → consumes CO₂ → pH spikes daytime.

Test Weekly

Liquid test kit (API, Tetra). Strips are inaccurate. Log results.