red eyed tetra has lost its red eye

Don't have any experience with the red eye tetra but color loss is usually a bad sign (at least for the neons, cardinals, rummy-nose, and black skirt tetras). I'd test your waters.
 
color loss is a sign of stress in the tetras I've mentioned, I'm guessing its the same for the red eye. Probably wasn't used to the tank yet and was scared.
 
Yeah, color loss is definetly a sign of stress. When I transferred my fish to a larger tank, my normally colorful Boesmani Rainbowfish turned pale as a sheet. Very interesting sight.
 
color change

Yeah, although this is kinda changing the subject, whenever my male kribensis gets pissed, he turns bright red then when he calms down he gets duller. like when hes guarding the nest.
 
yeah i happened again with one of the fishes. this time it didnt completly disappear but still had just a tiny bit of red showing. then later it was completely back.....weird how that can do that.
 
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