KoiLens guides
Clear, practical introductions to dealer facts, Scout and Body assessments, and the age terms you will meet while researching koi.
The koi buying guideResearch a koi before you contact the dealer.
Understanding Scout scoresRead the assessment hierarchy with confidence.
Tosai vs NisaiUnderstand which age may fit your goals.
Understanding Scout scores
KoiLens keeps its own assessments visibly separate from dealer facts. Scores help you compare supported listing evidence; they do not predict health, growth, show results, or resale value.
01 · Start with the hierarchy
02 · Compare like with like
Check dealer, price, variety, breeder, age, sex, size, listing freshness, and available media before reading assessments. An unavailable score means there is not enough supported information; it does not mean zero or low quality.
03 · Verify current evidence
Ask for current video, measurements, documentation, health information, and the delivered price. Use experienced or veterinary judgment for significant decisions.
Tosai vs Nisai
Tosai are in their first year; nisai are in their second. The right choice depends on your experience, pond, budget, and appetite for development uncertainty.
01 · First year
Tosai are typically smaller and often less expensive. Their future body, pattern balance, colour, and sex may be harder to judge, so current media and breeder context are especially important.
Keepers who enjoy development, can accommodate uncertainty, and have suitable growing conditions.
02 · Second year
Nisai usually show more body development and a clearer pattern trajectory. More visible evidence can improve comparison, but price and pond requirements commonly increase.
Keepers who want more developed evidence and are prepared for a larger koi and purchase commitment.
03 · Ask before deciding
Beginner buying guide
This short guide explains the terms and tools shown in KoiLens. It supports your research; it does not replace current dealer information, experienced judgment, or veterinary advice.
01 · Start with the listing
The farm or breeder named by the dealer as the koi’s producer.
The recognised colour and pattern group, such as Kohaku, Sanke, or Showa.
Lineage information attributed to the dealer or breeder. Ask for supporting records when lineage matters to you.
Japanese age terms include tosai for a koi in its first year, nisai for its second, and sansai for its third.
The listed length in centimetres. Confirm when and how the koi was last measured.
The dealer’s stated sex. Treat unknown or uncertain information as something to verify.
Dealer facts come from the listing or dealer. KoiLens keeps these facts separate from its own assessments and cannot guarantee that a listing is complete or current.
02 · Read the hierarchy
Scout and Body assessments are KoiLens research aids derived from the available evidence. Show potential is contained within Scout and is never shown as a separate score. Body has zero hidden influence on Scout. Assessments are not guarantees of future growth, show results, health, or value.
03 · Check the sale format
The displayed amount is the dealer’s listed price or POA when no public amount is supplied. Confirm availability and the full delivered cost.
The displayed amount can be an observed bid rather than the final price. Check the bid freshness, deadline, fees, and current dealer page before acting. An ended auction is not an available koi.
04 · Build a focused set
Save koi you deliberately want to revisit. Shortlist is your explicit local selection, not an automatic recommendation.
Select two to four koi to inspect their supported facts side by side. Use the images and dealer facts first, then read Scout and Body in their stated hierarchy.
05 · Verify before deciding
Inspect current dealer media at full size. For a significant purchase, seek judgment from an experienced keeper, koi professional, or appropriate veterinary professional.