Koi Care Guide

Whether you're a first-time koi keeper or an experienced pond enthusiast, this guide covers everything you need to keep your koi healthy, vibrant, and thriving year-round.

Pond Setup

Pond Size

Koi need space to grow. We recommend a minimum of 1,000 gallons for a small koi pond, with at least 250–500 gallons per adult fish. Depth should be at least 3–4 feet to protect fish from predators and temperature extremes.

Filtration

A high-quality biological and mechanical filtration system is essential. Your filter should be rated for at least 1.5× your pond volume to handle the bioload of koi. Never skip cycling your pond before adding fish.

Aeration

Koi require well-oxygenated water. Use air stones, waterfalls, or pond aerators to maintain dissolved oxygen levels, especially in summer when warm water holds less oxygen.

Water Quality

Test your water weekly and maintain these parameters:

  • pH: 7.0 – 8.5
  • Ammonia: 0 ppm
  • Nitrite: 0 ppm
  • Nitrate: Below 40 ppm
  • Temperature: 59°F – 77°F (15°C – 25°C)
  • KH (Carbonate Hardness): 100–200 ppm

Perform 10–20% water changes weekly to keep nitrates in check and maintain water clarity.

Feeding

Feed your koi 2–3 times daily during warmer months, offering only what they can consume in 5 minutes. As water temperatures drop below 50°F, reduce feeding significantly. Below 40°F, stop feeding entirely as koi enter a semi-dormant state and cannot digest food properly.

Choose a high-quality Blackwater brand koi food appropriate for the season — high-protein in summer, wheat germ-based in spring and fall.

Acclimating New Koi

  1. Float the sealed bag in your pond for 15–20 minutes to equalize water temperature.
  2. Open the bag and slowly add small amounts of pond water every 5 minutes for 15–20 minutes.
  3. Gently net the fish into the pond — do not pour bag water into your pond.
  4. Monitor new fish closely for the first 48 hours for signs of stress or illness.

Common Health Issues

White Spots (Ich)

Caused by a parasite. Treat with aquarium salt or an ich treatment. Raise water temperature slightly to speed up the parasite's life cycle.

Fin Rot

Bacterial infection often caused by poor water quality. Improve filtration, perform a water change, and treat with an antibacterial pond treatment.

Jumping or Flashing

May indicate parasites or poor water quality. Test water parameters immediately and inspect fish for visible parasites.

Seasonal Care

Spring

As water warms above 50°F, gradually resume feeding. Perform a thorough pond cleaning and check all equipment after winter.

Summer

Monitor oxygen levels closely during heat waves. Add aeration if needed. Feed a high-protein Blackwater brand koi food to support growth.

Fall

Switch to a wheat germ-based Blackwater brand koi food as temperatures drop. Remove leaves and debris to prevent water quality issues.

Winter

Stop feeding below 40°F. Use a pond de-icer or aerator to maintain a hole in the ice for gas exchange. Do not break ice by force.

Need Help?

Our team is always happy to answer your koi care questions. Contact us anytime or browse our FAQ page for quick answers.