Tetras Dropping Like Flies

I started out with 6 neon tetras. One, then another started hiding most of the time except meals. The one that had been hiding longer got a spinal deformity, and died. It took a few months for him to die. Then the other one, about a month later, had the same thing happen, and die. Now yet another one is showing the same symptoms. Any ideas as to what this is? Thanks!
 

Thanks so much for replying! I'll try to post a picture so you can see the symptoms.

After a while the blue stripe did turn yellowish,
I don't see a black lining I don't think,
Maybe they get a lump on the belly,
And the bent spine and leaving the school,
They also become very emaciated.

That's nice to know it's not contagious to other species, I was worried about my betta and BN pleco! Especially since the betta ate the eyes out of the dead ones.... 

The fish doesn't look very well, does it. Not all the symptoms will necessarily be present, but NTD will have several of them if not all. I would be inclined to act for the worst case scenario and assume it is NTD. If you put the affected fish down, the others might be safe.


Buy some clove oil, an old fashioned toothache remedy sold at the chemist shop. It comes in little bottles, perhaps inside a cardboard box. Next you will need a tub and a bottle/jar with a tight lid. Choose carefully as you won't be able to use them again. Put some tank water in the tub and place the fish in the water. Put 20 to 30 drops of clove oil in the bottle/jar (the amount depends on how big the tub is), add a bit of cold water and shake until the oil emulsifies. Pour the oil/water mix into the tub with the fish. Leave for a few hours. Clove oil knocks the fish out before killing it and if you remove it too soon, it could wake up. Waiting a few hours will ensure the fish is dead. Throw it in the bin or bury it if you can't face the bin option.
Clove oil stinks. You might want to use use rubber gloves.

That is the method that most people find easiest. The other methods are much worse for the fishkeeper 
Is there anyone who could do it for you?

If it is NTD, you could end up losing them all if you don't remove infected fish.......

It's not easy - and definitely makes you feel like a murderer!!  I know because I've just had to do it tonight to one of my Black Widow tetras who was really quite poorly (although I'm not sure with what - possibly dropsy).  The thing that made me feel better was thinking about saving the other fish from a similar disease and also the sick fish was obviously unhappy and probably suffering.  Using the clove oil is very humane and my poor fishy just "went to sleep" and hopefully didn't feel a thing        Still feel bad though....

Hope you manage to do the deed (or get someone else to do it) and the rest of your fish are fine 

Liz