Koi

Key Stats at a Glance

Overview

Koi are ornamental varieties of the common carp (Cyprinus carpio), bred in Japan for centuries for their striking colours and patterns. They are pond fish that can grow up to 60–90 cm and live for decades. Koi keeping is a serious hobby — they require a large, well-filtered pond and regular care, but reward their keepers with personality, longevity, and breathtaking beauty.

Pond Setup

• •A minimum pond volume of 3,000 litres is recommended for even a small group of koi.
• •Pond depth should be at least 1–1.5 metres to protect koi from temperature extremes and predators.
• •A high-flow biological filter rated for koi is non-negotiable — koi produce enormous quantities of waste.
• •A bottom drain with an external settling chamber significantly improves water quality.
• •UV sterilisers help control green water (algae blooms) and reduce pathogens.
• •Provide shade (water lilies, overhead netting) to prevent overheating in Chennai summers.
• •Install a net or heron guard to protect koi from birds and cats.

Feeding

• •Feed 2–4 times daily during warm months; reduce to once a day in cooler weather.
• •Koi pellets (high-protein in summer, wheat-germ based in winter) are the staple diet.
• •Supplement with watermelon, lettuce, orange slices, and prawns for variety.
• •Feed only as much as koi consume in 5 minutes — remove uneaten food.
• •Stop feeding if water temperature drops below 10°C (not typical in Chennai but relevant for hill areas).
• •Avoid feeding during the first week after new koi are introduced while they acclimatise.

Health Tips

• •Ich and koi herpesvirus (KHV) are serious concerns — quarantine all new fish for 4–6 weeks.
• •Anchor worm and fish lice are visible parasites; use appropriate pond treatments.
• •Ulcers and bacterial infections often stem from physical damage or stress; treat with pond-safe antibacterials.
• •Test pond water weekly — ammonia and nitrite should always be zero.
• •Koi are sensitive to chlorine and chloramine; always dechlorinate tap water before adding to the pond.
• •Spring and autumn are peak disease seasons due to temperature fluctuations — monitor closely.

Compatible Species