Introduction

Across Southeast Asia and parts of South Asia, one species quietly stands at the center of high-profit freshwater aquaculture—Climbing Perch, known locally as Koi (not ornamental koi). Its scientific name, Anabas testudineus, reflects a rugged fish shaped by evolution to conquer the most hostile freshwater habitats on the continent.

The story of Koi is intertwined with the rhythms of rural life. In the wetlands of Bengal, farmers say that Koi survives “where even frogs die.” In Thailand, villagers call it the “walking fish” because it can crawl over wet ground using its gill covers. In Cambodia, it is the fish that continues living inside cracked mud even after ponds dry. This resilience makes Koi one of the most dependable commercial species in tropical aquaculture.

During field visits in Bangladesh and West Bengal, what stands out is the confidence farmers show. One farmer near Mymensingh said, “If you give Koi water up to your ankle and feed equal to your palm, it will still grow.” This sentence captures the biological genius of the species—it is small, tough, air-breathing, omnivorous, tank-friendly, and extremely profitable.

With rising temperatures, shrinking water bodies, and climate irregularities, species like Climbing Perch represent the future of sustainable aquaculture. This guide explores the entire global structure of Koi fish farming, narrated in a pure human style, rooted in field observations and scientific clarity.

Natural Habitat & Behaviour

Climbing Perch evolved in shallow, warm wetlands—seasonally flooded rice paddies, marshes, lowland ponds, irrigation canals, and silt-filled ditches. These habitats are unstable, oxygen-poor, and fluctuate wildly, but Koi adapted so strongly that it not only survives—its thrives.

Key biological traits:

Breathes atmospheric oxygen through a labyrinth organ

Actively crawls over moist ground

Endures dense stocking

Remains alive hours outside water (farmers confirm this)

Handles water stagnation and turbidity

Grows fast in warm climates

Koi displays a mix of predator and omnivore behaviour. In nature, it feeds on insects, worms, crustaceans, algae, and organic debris. In captivity, it quickly adapts to pellets, making feeding economical.

Its alertness is unique. In tanks, Koi reacts instantly to shadows and surface vibrations, a survival mechanism ingrained through generations.

Climate Tolerance & Water Parameters

Ideal temperature:
26°C – 32°C

Survival tolerance:
18°C – 38°C

pH:
6.5 – 8.2

Dissolved Oxygen:
Very low acceptable due to air breathing.

Depth:
2.5 – 4 feet ideal for ponds.
1–1.5 m for tanks.

Koi prefers:

moderately turbid water

shaded areas

slow or stagnant water

warm microclimates

It dislikes:

overly clear water

sudden temperature drops

chemically treated ponds

deep unlit water

These preferences directly influence farming system design.

Pond, Tank & Advanced Farming Systems

Earthen Ponds (Traditional + Commercial)

Most common in India, Bangladesh, Myanmar.
Ponds maintained shallow (3 feet).
Weed cover improves comfort and feeding.

Cement / FRP Tanks (Modern Commercial Farming)

Most profitable and controllable system.
Tank sizes vary from 1,000L to 50,000L.
Koi tolerates high densities and structured feeding.

Biofloc Hybrid (NOT full biofloc)

Koi adapts to light floc density but becomes stressed in thick floc.
Hybrid floc improves growth if water clarity is maintained.

Backyard Micro Farming

Small concrete tanks or plastic tubs.
One of the best fish for household aquaculture.

Rice–Fish Integration

Koi hunts pests and insects in paddy fields.
Improves rice yield and water ecology.

Cage Culture (Emerging)

Used in Southeast Asia.
Growth fast but feed must be carefully managed.

Pond & Tank Preparation

Earthen ponds:
Dry completely. Remove sludge.
Apply lime only when pH < 6.5.
Add cow dung slurry to activate plankton.
Fill slowly to allow microbial balance.

Tanks:
Clean thoroughly.
Fill and drain once to remove cement residue.
Use organic bio-activators for microbial stability.

Shade:
Essential for reducing stress.
Coconut leaves, shade nets, bamboo screens used widely.

Seed Production & Fingerling Selection

Hatchery production now fully established across Asia.
Best fingerlings are:

4–6 cm

active, uniform

no injuries

responsive to surface movement

Acclimatization: Float bags → mix tank water → equalize temperature → release.

Koi fingerlings are hardy but size variation leads to aggression.
Strict grading is essential.

Stocking Density

Earthen ponds:
20,000 – 30,000 per acre (extensive)
40,000 – 60,000 per acre (semi-intensive)

Tanks:
300 – 400 fish per cubic meter (standard)
500 – 700 per cubic meter (intensive)
800+ per cubic meter (expert level with water exchange)

Koi tolerates high density due to strong air-breathing capacity.

Feeding Behaviour & Nutritional Needs

In natural habitats, Koi hunts insects, larvae, algae, and small aquatic organisms.

In farms, feeding transitions to:

28–35% protein pellets

homemade feed (rice bran + oil cakes)

chopped earthworms in early stages

slaughterhouse waste in some regions (legal restrictions apply)

Feeding pattern:

peak at dawn

moderate mid-day

strong at dusk

Farmers often synchronize feeding with shade movements in ponds.
Tank farmers report that Koi responds well to rhythmic feeding schedules.

FCR (Feed Conversion Ratio): 1.2 – 1.7 in well-managed systems.

Growth Cycle

Growth is strongly temperature-dependent.

Typical progress:

50–70g in 2 months

150–250g in 4 months

300–400g in 6 months

500–700g in 9–10 months

1kg+ in 12 months (high-quality feed)

Tank systems outperform ponds due to controlled feeding.

Cost, Economics & Profitability

Cost (1 acre equivalent or tank equivalent)

INR ₹1.8 – ₹2.7 lakh
USD $2200 – $3300

Selling Price

India: $4–7 per kg
Bangladesh: $4–6
Thailand: $5–8
Vietnam: $5–9
Middle East (Asian supermarkets): $8–12

Profit Margin

55% – 85%
(depends on feed and density)

Koi has one of the highest survival rates in freshwater aquaculture.

Health Benefits & Nutrition

Per 100g:

Protein 16–17g

Fat 2–3g

Very low cholesterol

Minerals: Phosphorus, Iron

Vitamins: B12, D

Known for:

recovery diets

muscle repair

immunity improvement

Bangladesh and Vietnam treat Koi as a medicinal fish in traditional diets.

Global Market & Export

Koi demand rising globally due to:

nutrition

ease of farming

low mortality

climate adaptability

Export mainly in frozen/gutted form.
Strong demand in:

UAE

Malaysia

Singapore

South Asian supermarkets abroad

Challenges & Solutions

Aggression in early stages

Solution: Grading every 10–15 days.

Ammonia build-up in tanks

Solution: Frequent partial water exchange.

Stress due to bright light

Solution: Shading required.

Sudden feeding drop in cold weather

Solution: Reduce feed, maintain temperature.

FAQs

Is Koi fish easy to farm?
Yes, one of the hardest, most beginner-friendly species.

Can it survive low oxygen?
Yes, it breathes air.

Tank farming profitable?
Very—one of the best for small-scale farmers.

Does it require high-protein feed?
Moderate protein works; high protein increases growth speed.

Conclusion

Climbing Perch (Koi fish) stands at the intersection of biology and profitability. Its resilience, feeding capacity, growth stability, and multi-system adaptability make it a cornerstone species of modern aquaculture. Whether farmed in ponds, tanks, biofloc hybrids, or integrated rice–fish systems, Koi offers stability and high return on investment. As global water scarcity increases, Koi’s biological strengths will make it even more important in sustainable fish production.

✍️Farming Writers Team

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