shrimp contains a lot of astaxanthin, which is why i feed it so much. the shell has the most of it. you'd get more if you bought the pure stuff though. up to you. i believe a lot of flowerhorn specific foods contain a decent dose aswell.
Astaxanthin does many good things. It brings out the red colors in your fish. It is also a powerful antioxidant. There are many more benefits of astaxanthin....google it. Good stuff...
Just a FYI - the makers of Naturose astaxanthin (Cyanotech Corp.) have not been producing or selling that ingredient for animal feed since March 2008. Under ideal storage temps, its shelf life is less than 1 year.
Do the math.