Neon tetras dying one by one

[Oonallee]

My neon tetras are dying one by one. I've had them 6 months and their appearance hasn't changed, water cond are the same gh 0 kh0 ph 6 nitrite 0 nitrate 20. But I have lost one a day for about a week. They appear fine

http://m.flickr.com/lightbox?id=6119749546

Any thoughts? I've treated with bactonex with no joy.

[Nev]

Did you read this post?
http://www.discusforums.com/forum/viewtopic.php?t=22893
Sounds similar (ish) hope it's not though, illusion prolly knows heaps more and with luck can help.

[Oonallee]

Hi nev yeh just did. Thanks for that seems to be the problem :(