Astaxanthin is a super antioxidant carotenoid that is found in krill oil. This powerful antioxidant provides exceptional protection against oxidation, greatly extending the life of krill oil.Fish oil, on the other hand can oxidize, spoiling its benefits and releasing free radicals in the body.staxanthin is found in microalgae, krill and in such seafood as salmon, trout and shrimp. It's a carotenoid, which means it's related to vitamin A, beta-carotene, lutein and zeaxanthin. Astaxanthin may have antioxidant and anti-inflammatory properties.