Astaxanthin

Astaxanthin in fish food: koi colour research, its limitations, and the distinction between a listed pigment and proven product performance.

Ingredient Directory›Astaxanthin

Ingredient & nutrient profile

Astaxanthin

A pigment listed in fish foods, with evidence that must be read by species, source and formulation.

AdditiveFishKoi
AX
AstaxanthinNutritional role • Research • Practical context
SpeciesKoi evidence
ScopeIngredient and nutrient context
AssessmentInitial evidence summary
Sources checked23 September 2026
Nutritional role

What it contributes

Astaxanthin is used as a pigment ingredient in the foods linked below. This profile focuses on colour evidence. A colour claim should be evaluated separately from claims about immunity, growth or overall health.

Species and formulation

Read it in context

The linked experiment studied koi in controlled freshwater tanks. Hikari Betta Bio-Gold, Goldfish Gold and Excel list astaxanthin on their US manufacturer pages. Those listings establish declared presence only. They do not establish an effective amount or equivalent performance across species.

Research

What the evidence shows

Kim and Lee (2014) reported greater skin redness with a Carophyll Pink diet than with control feed after eight weeks. There were two replicate tanks per diet. The study tested an experimental diet, not the Hikari products listed here. See the full study entry for design and limitations.

Limits and safety

Before changing the diet

This entry does not establish a supplement dose, lifelong safety threshold or benefit in bettas, goldfish or marine fish. Ingredient studies cannot show whether adding a supplement to an existing formulated food is appropriate. Colour intensity is not a stand-alone measure of fish health.

Food labels

Questions worth asking

Check the intended species, the source and amount of pigment if declared, and whether evidence concerns the finished product. Do not assume that a named pigment guarantees a particular colour response. The source and amount in these retail foods were not established by the manufacturer ingredient lists reviewed.

Connected evidence

Explore the study

The linked study identifies the fish species, feeding method and limits of the evidence.

Koi · 2014 · Two replicate tanks per dietSpirulina and pigment sources in koi: an eight-week feeding studyRead the study summary, methods and limitations.
Sources

References and review scope

  1. Kim YO, Lee SM. Effect of Dietary Carotenoids Sources on Growth and Skin Color of Red- and White-colored Fancy Carp Cyprinus carpio var. koi. Korean Journal of Fisheries and Aquatic Sciences. 2014;47(6):790–795. doi:10.5657/KFAS.2014.0790.
  2. Hikari Betta Bio-Gold US manufacturer declaration
  3. Hikari Goldfish Gold US manufacturer declaration
  4. Hikari Excel US manufacturer declaration

This is an initial, source-linked overview, not a systematic review or a product endorsement. Study-specific access limitations are stated above.

Research on this ingredient

Common_carp

Astaxanthin and experimental bacterial challenge in common carp

One study with 3 reviewed arm or dose connection(s).

Arm astaxanthin_100_mg_kg_feed

Astaxanthin and experimental bacterial challenge in common carp

Direct · common_carp. Common carp in dietary astaxanthin groups, followed by an experimental Aeromonas hydrophila challenge.

Tested form: Astaxanthin incorporated into feed; source preparation not established in the reviewed abstract. Dose: 100 mg/kg feed (Milligrams astaxanthin per kilogram feed; oral feeding). Duration: Four weeks of feeding before bacterial challenge. Comparator: Feed without added astaxanthin.

Measured finding: Some immune and blood measures increased; not all growth measures improved. Challenge mortality was reported as 35%, 10% and 20% for the 25, 50 and 100 mg/kg groups respectively. Control mortality is not stated in the reviewed abstract.

Limitations: Species-specific challenge experiment. Astaxanthin preparation and sample details are not established in the abstract; no automatic generalization to other ornamental fish or doses.

Abstract reviewed · Checked 2 October 2026 · Evidence.pet study summary · Primary source

Arm astaxanthin_25_mg_kg_feed

Astaxanthin and experimental bacterial challenge in common carp

Direct · common_carp. Common carp in dietary astaxanthin groups, followed by an experimental Aeromonas hydrophila challenge.

Tested form: Astaxanthin incorporated into feed; source preparation not established in the reviewed abstract. Dose: 25 mg/kg feed (Milligrams astaxanthin per kilogram feed; oral feeding). Duration: Four weeks of feeding before bacterial challenge. Comparator: Feed without added astaxanthin.

Measured finding: Some immune and blood measures increased; not all growth measures improved. Challenge mortality was reported as 35%, 10% and 20% for the 25, 50 and 100 mg/kg groups respectively. Control mortality is not stated in the reviewed abstract.

Limitations: Species-specific challenge experiment. Astaxanthin preparation and sample details are not established in the abstract; no automatic generalization to other ornamental fish or doses.

Abstract reviewed · Checked 2 October 2026 · Evidence.pet study summary · Primary source

Arm astaxanthin_50_mg_kg_feed

Astaxanthin and experimental bacterial challenge in common carp

Direct · common_carp. Common carp in dietary astaxanthin groups, followed by an experimental Aeromonas hydrophila challenge.

Tested form: Astaxanthin incorporated into feed; source preparation not established in the reviewed abstract. Dose: 50 mg/kg feed (Milligrams astaxanthin per kilogram feed; oral feeding). Duration: Four weeks of feeding before bacterial challenge. Comparator: Feed without added astaxanthin.

Measured finding: Some immune and blood measures increased; not all growth measures improved. Challenge mortality was reported as 35%, 10% and 20% for the 25, 50 and 100 mg/kg groups respectively. Control mortality is not stated in the reviewed abstract.

Limitations: Species-specific challenge experiment. Astaxanthin preparation and sample details are not established in the abstract; no automatic generalization to other ornamental fish or doses.

Abstract reviewed · Checked 2 October 2026 · Evidence.pet study summary · Primary source

Goldfish

Astaxanthin and rearing system in goldfish colour

One study with 1 reviewed arm or dose connection(s).

Arm primary-astaxanthin

Astaxanthin and rearing system in goldfish colour

Direct · goldfish. 120 juvenile goldfish in 24 aquariums, studied for 56 days.

Tested form: Astaxanthin-supplemented food; chemical source and preparation not reported in the reviewed abstract. Dose: Not reported in the reviewed abstract (Food inclusion; exact basis not reported in the reviewed abstract). Duration: 56 days. Comparator: Unsupplemented food and clear-water rearing.

Measured finding: Both supplementation and biofloc increased redness, yellowness, and skin carotenoids. No effects on weight gain, survival, or feed conversion were reported; no system-by-diet interaction was detected.

Limitations: Juvenile aquarium production conditions. Colour is not a general-health endpoint; one amount and duration were tested.

Abstract reviewed · Checked 25 September 2026 · Evidence.pet study summary · Primary source

Products listing or mentioning this ingredient

10 products linked through reviewed ingredient occurrences from manufacturer declarations or partial editorial summaries. Whole-label verification may remain pending. An ingredient’s presence alone does not establish a nutritional outcome.

  • Hikari Betta Bio-Gold Staging pilot: Hikari Betta Bio-Gold, US 2026-09; United States; manufacturer declaration Bettas, Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Hikari Oranda Gold Hikari Oranda Gold, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Goldfish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Hikari Sinking Goldfish Excel Hikari Sinking Goldfish Excel, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Goldfish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Color Enhancing Saki-Hikari Color Enhancing, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Fancy Goldfish Color Enhancing Saki-Hikari Fancy Goldfish Color Enhancing, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Goldfish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Growth Saki-Hikari Growth, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera Betta Granules Sera Betta Granules, editorial ingredient summary 2026-09-24; ; partial summary Bettas, Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera Immune Probiotic Granules Sera Immune Probiotic Granules, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera San Color Flakes Sera San Color Flakes, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera San Color Granules Sera San Color Granules, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope