Yeah I have wondered too if they have some sort of internal parasites or something. They feed well just like any other Cyprinella they just always look thin. I am hoping that maybe if they manage to spawn and grow up under my water conditions too that my captive raised ones may fair better, that is of course if they spawn.
Gerald do you think they may eat more algae than other cyprinella sp? that was another thought I had that my usual diet of mostly frozen blood worms, frozen mysis, flakes, and sinking shrimp pellets (this all gets put in my stream tank in ample supply every other day) is not enough for these.
All the other fish in the tank (various darters, many different cyprinids, a huge sharpfin chubsucker, madtoms I never see, some Enneacanthus sunfish, and even a golden topminnow) all seem very fat and happy. I know calling this my "stream tank" is not appropriate for all of these species. It is kind of the everything that will get along tank. It is L shaped and 165 gallons stretching a total of 11.5 feet from back corner on one end to the back corner on the other. The front of the tank is more like 8.5 you loose distance in that back corner. There is quite a variety of habitats and varying flows and substrate so all the fish seem to find their place and I just spread a lot of food all over the tank.
I feed the group of about 20 that had been alone in a 75 by themselves the same mix of foods. Those got moved outdoors yesterday so if algae is needed in the diet they will have plenty now.