Josh--those Redlines have a lot of black. Check out this one from a friend's tank. Zero red in him, or yellow for that matter! You can see a small portion of dorsal fin a typical Redline in the bottom right corner for comparison.
Gerald--I haven't kept Candy's but would guess they are very very similar to Kanawha's as far as how they'd do in captivity. I got my Kanawha last Fall. He's doing great and competes very well with a lot of much more food aggressive species. I feed my tank once a day, but slam it full of blackworms, or a mysis/bloodworm combo. Haven't seen any 'withering away' at all. I believe Derek has had similar results with Variegates slowly declining. I've never kept them but am curious to see if my ~3 months in quarantine---which also allows them time to adjust to captivity in a less competitive feeding environment----gives them the skills they need to survive in my highly competitive 150.
Additionally, where I saw Kanawhas and Candys in the wild, they had [what appeared to be] very little competition from neighboring species of darters, or even shiners for that matter. So I think it is fair to say that even mild competition throws them off their feeding. Redlines, on the otherhand are a very feisty feeder in streams with lots of other darter/shiner species which makes them excellent additions to a community stream tank.
I've gotten sub-adult/adult Bandeds and Greensides that have failed to thrive once I brought them home. However, I have 1 Greenside and 2 Bandeds that were all ~1" when I collected them and are thriving in the 150. I also attribute that to having the time to adapt to captivity and learning to be a little more aggressive feeders and less flighty than they usually are in the wild.
I would really like to try my hand at some Variegates to see if my long acclimation to captivity helps, or if they're just poor specimens to keep in captivity in general. Maybe we aren't providing them with something obvious? (Much to the same tune that oceanic species like tuna, mahi, and Great white & Tiger sharks historically failed in captivity before we realized vertical walls were the enemy).
If anyone wants me to explore my theory of Variegates in captivity with a prolonged introduction in a QX tank, I'm happy to receive an early xmas gift!