Ok so I have this 5 gal tank in my dorm room, 3 neons and 1 cory catfish. I have had them since august and things have been going great. I went home last night and fed my fish before I left. I turned the light off too. So I just got back like 10 min ago and turned the light back on and fed them again. I was gone for ~ 18-20 hrs. My neon tetras were like pale white, no red at all and on one I could see a little blue, the others I could not make any blue out. My filter has been going and I dont think I have any ammonia problems I did a test 3 days ago.
What do you think happened?
Thanks
-Gabe

Update:
Hey all of the sudden the color has returned, one of them is a little less red but the fish are colorful again
I did some research and light affects the tetras color
http://jcs.biologists.org/content/88/5/663.full.pdf
check it out it actually was really interesting
Take care
Go Big Red