Colourless Black Skirt Tetras

Do they swim around much or seem to hover most of the time?

I notice with tetras that more plants really help to perk them up since they have cover to hide if they need to.
 
This get's more interesting
The
 
It gets moe interesting.
I forgot to turn on the tank lights the other day before leaving for work. When I came home the Black Skirts were nicely colored with dark black fins and stipes. I thought all was well after the large water change. I turned the lights on and kept an eye on them for the next little while and I swear I could see them fading over that short time. I turn the lights off and the color comes back, lights on and they fade away. It is not an instant fading, but happens fairly quickly.
The light bulb was a Hagen Aqua-Glo.
Does this make any sense?
 
More than a few fish that I know of like low light vice something bright.
 
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