Asagi Koi Care Guide: Blue-Scaled Heritage Variety for Ponds

The Asagi is one of the oldest and most refined koi varieties, prized for its blue reticulated scale pattern and contrasting red-orange hi markings along the belly and fin bases. This asagi koi care guide draws on the hands-on experience we have built at Gensou Aquascaping, 5 Everton Park, Singapore, helping local pond enthusiasts appreciate this understated heritage variety that rewards patient keepers with stunning colour development over the years.

What Makes a Good Asagi

Quality Asagi display an even, blue-grey netting pattern across the dorsal surface, created by lighter-coloured scale centres against darker edges. This reticulation should be symmetrical and uniform, without missing scales or discoloured patches. The hi (red-orange pigment) appears on the cheeks, pectoral fin joints, and belly. Clean, unblemished white skin on the head completes the picture. Specimens where hi creeps above the lateral line are considered less desirable, as the blue net pattern is the variety’s defining feature.

Choosing and Buying Asagi

Asagi are among the more affordable heritage varieties. In Singapore, pond-grade juveniles of 15-20 cm typically sell for $50-150 SGD, while well-bred tosai from recognised Japanese bloodlines command $200-500 SGD. When selecting, hold the fish in a viewing bowl and examine the scale pattern from directly above. Even, tight netting with no bare patches indicates good skin quality. Avoid fish with excessive hi spread or muddy blue tones, as these traits tend to worsen with age rather than improve.

Pond Setup and Environment

Like all koi, Asagi need spacious ponds with a minimum volume of 3,000 litres. Depth of 1.2-1.5 metres offers thermal stratification that benefits fish comfort in Singapore’s heat. Partial shading is important because prolonged direct sun at tropical latitudes accelerates algae growth and can cause the blue scales to fade. A well-planted pond margin with emergent species like Cyperus or Thalia provides natural shade while also helping to absorb excess nutrients from the water.

Water Quality for Colour Preservation

Asagi colouration is particularly sensitive to water quality. High nitrate levels above 40 ppm can dull the blue netting and muddy the hi markings. Maintain ammonia and nitrite at zero through robust biological filtration, and keep nitrate under 25 ppm with regular 10-15 percent weekly water changes. Singapore’s PUB tap water requires dechlorination to remove chloramine before adding to the pond. pH should sit between 7.0 and 7.5, buffered with oyster shell or coral rubite in the filter if needed.

Feeding for Blue and Red Development

A high-quality colour-enhancing pellet containing spirulina supports the blue tones, while carotenoid-rich ingredients like krill meal and astaxanthin deepen the red hi markings. Feed moderately; overfeeding leads to fat deposits that distort body shape and push scales apart, ruining the net pattern. Two to three small meals per day work well in Singapore’s warm climate, where koi remain active and metabolically engaged throughout the year. Supplement with fresh shelled peas or watermelon occasionally for fibre and hydration.

Hi Development and Seasonal Changes

In temperate Japan, Asagi hi intensifies during warmer months and fades in winter. Singapore’s consistently warm temperatures of 28-31 degrees Celsius mean hi expression stays relatively constant year-round, which can actually work in your favour. However, without a cool season to reset pigment cells, some Asagi develop creeping hi that gradually covers more of the body. This is a natural genetic tendency that you cannot fully prevent, but selecting fish from bloodlines known for stable hi boundaries helps. Viewing your koi from above during routine feeding lets you track any changes month to month.

Common Health Concerns

Asagi are hardy koi with no variety-specific health issues. Standard pond-keeping practices apply: quarantine new fish for two weeks, maintain excellent water quality, and treat parasitic infections early with salt or appropriate medications. Their lighter skin makes ulcers and lesions visible sooner than on darker varieties, which is an advantage for early detection. Inspect fish regularly during feeding for signs of flashing, lethargy, or appetite loss, and act promptly if anything looks amiss.

Related Reading

• Bekko Koi Care Guide: Simple Two-Colour Elegance in Your Pond
• Butterfly Koi Care Guide: Long-Finned Grace in Your Pond
• Kohaku Koi Care Guide: The Classic Red and White Variety
• Koi Fish Care Guide: Pond Basics and Indoor Tank Considerations
• Koi Fish Care Guide for Singapore: Ponds, Feeding and Health