While I realize that this is an old thread, I think that some of you (Tom & Jamie) may find this interesting.
In the study previously linked to the researchers stated:
Our data show that a diet low in carotenoids is sufficient to maintain both coloration and innate immunity in Midas cichlids.
IMO the following is rather clear evidence that when discussing carotenoid content (both type & quantity) the term "low" is certainly open to interpretation.
The following male amph was purchased on March 21st of this year, so just over 30 days ago. This male, along with his siblings all appeared to be xanthic morphs. While my camera is an old (and low quality) point & shoot I think that everyone would agree that in the before photos this fish appeared to have a yellow base color. In person, he was lemon yellow. All of these photos were taken with the same camera settings, in the same tank, with the exact same background, substrate, and lighting. The male shown below is approx 10 months old.
In approx 30 days this fish transformed from what appeared to be a lemon yellow xanthic morph, to what most would refer to as a common creamsicle morph. The only difference over the past 30 days was a change in diet. His previous diet was a low cost generic type farm feed (generic fish meal, soybean meal, blood meal, feather meal, etc) to a more premium food. (NLS)
Before:
After 30 days:
Before:
After 30 days:
Before:
After 30 days:
While I suspect that this young male is far from finished morphing in color, from here on in the vast majority of those changes will be determined by his genetics.
I think that this rather short 30 day snapshot paints a pretty clear image as to just how much the quality & quantity of carotenoids can play a role in the overall coloration of an amphilophus kept in captivity.