http://en.wikipedia.org/wiki/Astaxanthin

I hear that there is a type of this substance used to make goldfish turn red. Not suprising, considering it is a food dye.
My question is: Can goldfish tolerate the type of astaxanthin that has been treated to be digestable for it's antioxidant qalites?
I realize that cancer is one of the causes for death in goldfish, and I'm certain it would help, if gven in tiny doses. What can anyone tell me about this, in relation to cancer or otherwise.