Pre-Fab 600-Gal Pond for Koi: Too Small, Build Custom

Want 3–4 koi + goldfish in a 600-gal pre-fab (87.5" dia). Zone 6. Manufacturer says it's fine. Is it?

Manufacturer Is Wrong

Koi need 500–750 gal EACH long-term. 600 gal total = 1 koi max. 3–4 koi = 2000–3000 gal minimum. They grow to 24–36". In 600 gal, they stunt, suffer, die early.

Pre-Fab Ponds Are Generally Undersized

• Shallow (often <24"). Koi need 3–4 ft for winter temp stability.
• Integrated filters are inadequate for koi bioload.
• Hard to plumb proper bottom drain/skimmer.

Build It Right: EPDM Liner

1. Dig 10x15 ft, 3.5–4 ft deep (zone 6).
2. Underlayment + 45 mil EPDM liner.
3. Bottom drain + skimmer + external bead filter or bakki shower.
4. Air pump + de-icer for winter.

Koi Are a 40-Year Commitment

They tame, recognize you, live decades. Give them the home they deserve. Start with 3 koi in 2500+ gal. You'll never regret the effort.