The red carotenoid canthaxanthin is approved by EFSA at a concentration of 100 mg/kg feed for ornamental fish in feed.

Canthaxanthin is considered of no concern for genotoxicity. Considering the oxidative susceptibility of carotenoids, the use of canthaxanthin at the proposed maximum concentration in feed will not result in a substantial increase in canthaxanthin concentration in the environment and consequently does not pose a risk to the environment. Canthaxanthin has the potential to enhance the skin pigmentation of ornamental fish. 

Download full report (PDF): Scientific opinion on the safety and efficacy of canthaxanthin as a feed additive for poultry and for ornamental birds and ornamental fish [EFSA Journal 2014;12(1):3527 [24 pp.]. doi:10.2903/j.efsa.2014.3527]