
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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