FishForums.net Pet of the Month
🐶 The Poll is Open! 🦎 Click here to Vote! 🐰


Fish Fanatic
Jul 14, 2002
Reaction score
Hi all,
I know I haven't been on in a while but I have a quick question. Some of my neon tetras' tails have gone a funny white colour. (where the red bit is). It has got worse over the last while but doesnt seem to be affecting them. It has gradually got worse and looks as though the red has "run out" or something and it covers most of the area on their tail. We had a death last week (a molly) but i checked carefully for signs of disease but there didnt seem to be anything unusual. In the last few days I have noticed that a guppy of mine has started to look ill. It's as if the muscles in its tail arent working, and so his head is level but about half way down his body it starts to curve down the way and his tail is alsmost vertical to the head. All parameters are ok (pH 7.2) but I haven't been cleaning out the tank as often as I should really ;) Any ideas what to do?


TFF Founder
Retired Moderator ⚒️
Jan 17, 2002
Reaction score
Hi James welcome back!

Whats the lighting in your tank like, I know that my cardinals colours are really bright in my tnak but in the shop they were duller. Also I find if they are shocked the red stripe will almost disappear, eg if i turn the light off and then on. So perhaps as you mentioned less than perfect water conditions could be affecting them, stressing them and generally not being too good, neons are some of the most sensitive tetras.
Neons don't live too long either so it could just be old age, they also get quite a few illness's and this could be one of them, I've not kept neons though! So thats about all the help I can give on that front!

Guppies back into my own territory now! I've seen the problem you describe but only ever in guppy fry, I presumed it was some genetic fault with them and I found within abou 3-5 days of noticing an ill guppy it would be dead. I did lose a lot of fry this way but my adults were not affected which perhaps suggests it is not contagious. I am afraid I know no cure and about 20 of my little guppies died :-( It could also be old age guppies don't live very long and when you get them from the shops they are usually a couple of months old anyway, and their lifespan is about 18months.

Sorry couldn't be of more help! :X


Fish Addict
Jul 21, 2002
Reaction score
Never kept them, but I'd read neons can live more than to 10yrs...

Sounds like neon tetra disease (go figure). It affects the muscles. They say it can affect other fish, not sure if includes guppies, kinda sounds like it, tho.

Doesn't look good; apparently there's no cure. :/

This article may have some suggestions (separate ill fish!).

(It notes that cardinals are immune.)

Most reactions