I have a school of eight neon tetras in my tank and three mickey mouse platys. They've been in for about a week now. They're all eating and they school together about half the time. I feed them tetramin flakes most of the time with once a week treats of brine shrimp and another frozen food. I've started trying to give them some lettuce but the ingrates are so far uninterested.

My water parameters are:
pH: 7.5
Temp: 80^o F or 26.7^o C
Ammonia: 0
Nitrites: 0
Nitrates: ~5ppm

Immediately after the last batch of neons were added they were as usual very pale, nearly white, as they always are when I add some. Three of them returned to full color within a couple of hours. The smallest one did not, and still has not. He's not as pale as when first put in but his colors are washed out and not vibrant like the others. He also looks to be breathing harder than the rest and not as plump. I hate to say it but does this sound like neon tetra disease?

how long have they been in the tank for?

Six days to be exact.

No.

The poorly named "Neon Tetra Diseae", (poor because it can affect many species and not just tetras), is caused by an infestation of sporozoan parasites. These live in the muscle of the fish. As they grow they start to become visible through the skin as a pale patch. As they continue to grow, their presence distorts the spine giving the fish a bent appearance. Eventually the fish is so crippled that it is no longer able to swim or look after itself and succumbs. From first appearance to death can take months, a lot depends on the species and things like temperature.

What you describe sounds more like stress. If it was not like that in the shop, then it probably has got upset by the move. It could also have been damaged in netting/bagging/transport of course.

If you have no live plants, switch the lights off for a few days. That often helps settle new fish.

I've been watching him for any sign of deformity and so far he looks fine. He's improved some what in the last 48 hours, he's not hiding in a cave any more and his colors are improving. He was easy to pick out from the rest of the neons before but now I have to really look at them to find him. I'll keep an eye on him for now and hopefully he'll continue to perk up.

I'm just a bit nervous because I've heard of entire tanks full of neons being wiped out by this parasite.

Sounds like you've just got an overly sensitive example there then.

NTD used to be a really rare thing, but the poor hygiene of the intense farms in Asia has raised it's profile. It is still, however, uncommon.