When the stomach contents of wild Texans have been analyzed, approx 80% has been algae, and plant material.
This would suggest to me, that a pellet high in spirulina would be a good choice.
I am keeping carpintus outside this summer, I am not feeding at all, so they are living mostly on algae, and whatever falls in. They look better than the ones I've kept inside.
Most fish kept outside look better due to the natural rays of sunlight. Even fish raised on low quality farm feed will generally look far better when kept outdoors under natural sunshine, than those fed the exact same diet but raised indoors.
While algae meal, spirulina, and various other aquatic micro-algae all play an important role in the health of a fish, you cannot compare what an algae eating fish in the wild consumes vs one fed in an aquarium, even if large amounts of aquatic plant matter are included in the diet. The gut analysis of wild fish is highly subjective, in that many times a lot of what is being consumed cannot be identified (beyond a mix of mush) unless the food was consumed almost immediately before the gut analysis took place. What might appear on the surface to be mostly "algae & plant matter" more than likely contained numerous small invertebrates, larvae, nymphs, snails, mites etc found within the algae itself. This holds true for even the most herbivorous of cichlid species. They aren't living & growing off of just plant matter. One also has to compare the life stage of the fish, some fish start out life feeding in the algae beds, and as they mature shift more to meat eaters, at least if/when smaller prey is available.
Same holds true for an outdoor pond setting, typically there will be a lot more available in the way of small insects, larvae, etc, than just algae. Also, fish in outdoor ponds tend to feed continuously from sun up to sun down, and are not subjected to the same limited quantity, and feeding schedules, as fish kept in captivity. With only a once or twice feeding per day, filling a fish up with mostly algae, kelp, or spirulina is not going to give nearly as good results in growth or overall health as feeding a diet that is more balanced with animal protein, such as fish, krill, shrimp, etc as the main components.
