Astaxanthin

Just wondering how effective this is?

How good is it really at improving colouring of fish and does having it in food help in any other way.

I was looking up about it and found it used to colour salmon but info I found pointed to red colouration so can see why it would be good for salmon.

I know that levels of astaxanthin are naturally found in the food of fish but do the fish that eat it really need it?

People are promoting a lot of things in foods these days and bumping the prices up.

Is it already in fish foods anyway but never promoted and now they have seen another use for it they are creating a selling point to up prices?

This is actually an interesting thing to bring up, so giving it a bump.
Wish I had some spare time to do a bit of research into it