Aquapedia summary
金剛石 is a 2026 Masaharu Tarumi line built from a mixed-cross base that includes 和墨 (Wazumi) × ネプチューン (Neptune) × フロマージュ (Fromage) and other material. The strongest specialist-publisher source located says Tarumi is selecting toward yellow pigment plus body external light (体外光) while also pursuing long-fin expression.
The same source states that the line was first released on 2026-05-03 through a 夢中めだか (Muchu Medaka) Instagram Live. A later secondary market report describes black/sumi appearing over the yellow/external-light expression. That sumi description is useful phenotype context, but is not yet promoted to a primary-verified defining trait.
Important normalization point: Japanese 金剛石 ordinarily romanizes as Kongōseki, but medaka sources explicitly present this strain as 金剛石（ダイヤモンド） and one contemporary medaka-market source says the displayed reading is Diamond. Aquapedia should therefore store 金剛石 as the canonical Japanese written name, Diamond / ダイヤモンド as the documented strain reading/display alias, and Kongōseki / Kongouseki / Kongoseki as search aliases rather than silently replacing the documented display na
Evidence notes
Pisces / 株式会社ピーシーズ — 「金剛石（ダイヤモンド）」, published 2026-06-21
This source states that Masaharu Tarumi of Saijō, Ehime developed the line from a base involving 和墨 × ネプチューン × フロマージュ and others, prioritizing yellow pigment and body external light, while aiming to move the line toward long-fin form. It also states the strain was first released on 2026-05-03 during a 夢中めだか Instagram Live.
Aquapedia status: verifiedsecondary. Pisces is a specialist publisher documenting the breeder and strain, but this page is not Tarumi's own account.
Image provenance
Do not copy or claim ownership of third-party images. The Pisces article contains three documented reference images photographed at 丸良めだか's facility. Aquapedia should retain source links/credits only unless reuse permission is obtained.
Credit context from Pisces: fish obtained by 丸良めだか; photography performed at 丸良めだか's breeding facility.
Genetics / cross-breeding implications
Do not model 金剛石 as a simple two-parent Mendelian strain. The published description explicitly calls it a line built on a multi-strain mixed-cross base and says selection is still being directed toward long-fin expression. For the Aquapedia breeding/game genetics layer, represent the following as phenotype-selection components rather than proven single-gene inheritance until stronger breeder data exists
For now, treat Silver as a segregating phenotype state within the 金剛石 line, not as an independent fixed strain. The reported silver × silver → yellow-expression observation should remain a low-confidence breeding-rule candidate. Do not assign fixed inheritance percentages, dominance/recessiveness, or guaranteed offspring outcomes without breeder records or controlled-cross evidence.
Open verification tasks
1. Locate Tarumi's own post/reel announcing 金剛石 and preserve the exact breeder wording.
2. Locate the archived 2026-05-03 夢中めだか Instagram Live or a direct release post.
3. Determine whether “Diamond” is the breeder-designated reading or a distributor/publication reading.
Aquapedia decision
Add and retain the strain as a source-backed 2026 Tarumi line. The evidence now supports an additional reported segregation note for the silver / low-yellow expression, but not promotion of “Silver Type” to a fixed formal subtype. The record should not claim a fixed long-fin genotype, a complete pedigree, or a formal silver subtype yet.
Public research references
Listed research leads are not automatically supporting evidence for every individual claim.
No eligible public supporting URLs are attached to this summary yet.