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.
Declared ingredient

Foods listing astaxanthin

These are manufacturer ingredient declarations, not product trials or endorsements. The linked koi experiment does not establish benefits in bettas or goldfish.

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.