Good find Tom, thanks!
It seems both of you missed the main points in that study, and/or don't fully grasp the role that
natural color enhancing agents play in the diet of fish, all species of fish. It isn't just about color.
Certainly some species of fish will be able to utilize higher concentrations of certain carotenoids for both color and/or immunity, but that doesn't equate to stating that one needs to, or even should, feed less carotenoid levels to a midas, vs a guppy.
The authors clearly state that with regards to color enhancement their results may have been affected by complex interactions among the carotenoids used. (which is sometihing that I alluded to earlier) and with regards to immunity they also clearly stated that their negative results may be attributed to the fact that they used
in vitro assessments of innate immunity - and explained how/why that could influence their results.
This study also didn't take into account the dietary carotenoid requirements of this species in a juvenile stage of life, which could in fact vary greatly from sexually mature adults.
What you both are suggesting, is that while eating 3 carrots daily has been proven to be good for ones health, no one should eat 5 carrots, as to date there isn't any data to prove that eating the 4th & 5th carrot will offer any extra health benefits. And the down side to eating those two extra carrots would be ......?
The only goal of this study was to examine the potential trade offs, between coloration & immunity. Nothing more, nothing less.
And as I mentioned previously much of this is still open to interpretation due to the types & levels of the carotenoids used, and the potential interaction between each group.
The bottom line is, the OP of this discussion doesn't need to add any "extra" color enhancing agents, or carotenoids, to his fishes diet of NLS.
