Black Blotch?

[Katty]

Some back story: I set up (March 1st) and cycled (April 3rd) a 5.5 gallon tank using pure ammonia and media from my ten gallon, and the 5.5 gallon tank is serving as a temporary quarintine to 9 green neons who will be moved into the 10 gallon once they prove healthy. A couple of the larger neons came with ich so I started treating the tank with Quick Cure at 3 drops one day, 2 drops the next, then 3 drops the next, then a 25% water change and repeat. I've also raised the temperature to 84 F. The ich is clearing up, but I noticed that one of the smallest green neons has a black blotch in the middle of it's green stripe. I'm not sure what it is but if it's anything bad I want to nip it in the bud. He seems to have had it since I've got him (it's been over a week now) but I've never seen anything like this, disease or otherwise, and it's only on one side.

Tank size: 5.5 gallons
pH: 7.4
ammonia: 0
nitrite: 0
tank temp: 84 F
Fish Symptoms : The fish in question has a large, black splotch interrupting the blue stripe down its right side. The spot is only on this fish, and only on its right side. He is also one of the smallest fish, at 1-2 cm. Otherwise, he seems to be healthy and eating.
Volume and Frequency of water changes: 25% every 3 days
Chemical Additives or Media in your tank: Just filter floss
Tank inhabitants: 9 Green neon tetras
Exposure to chemicals: Half dose of Quick Cure daily
Digital photo:

I could not take a picture of the fish because my camera is horrible and they move before it can focus. So I photoshopped this up. The fish in question is about 1-2 cm long and has this black spot on his right side. It appears to be flat from the side. It looks just like the picture.

So is it just a funny marking or could it be something bad?

 

[WILDER]

Black patches or blotches can be a number of things from ammonia burns that are healing, parasties, fish tb, cancer, cell damage.

Does the fish show any of these symtoms.
Red area will look bleached out. Or a milky substance on the red stripe area.
The blue area will have a yellow sheen to it.
Black linning around the tail area.
Fish will leave shoal.
Fish will act restless.
Fish will swim oddly.
Fish will become thin.
Bent spine.
Dropsy and popeye in later stages.
Lumps that go to a point in the tummy region.

 

[Katty]

All of his colors are vibrant and his body isn't malformed in any way, the only physical abnormality is the black spot. I have noticed that he doesn't stay as close to the shoal and will "wander off" towards the fake plants alone, and hang in and around the leaves and hide.

 

[Katty]

I've been reading up on what it could be and ran across Neon Tetra disease. I've been worrying myself sick about it, could that be it? It seems its near impossible to get rid of. I've read it typically shows up as white patches though and I haven't seen any on my fish, but I'm still worried... I've thought about euthanizing this one just so if it has anything it won't carry on to ruin the others, but I can't bring myself to kill something with my own hands, especially if I don't know if there's anything actually wrong in the first place, let alone neon tetra disease.

 

[WILDER]

I've had ntd about 5 years ago.

The first signs of ntd are bleached out red stripe area, or a milky substance on the red stripe area.

Has the neon been kept with snails.
Has your tank ever had an ammonia reading.
Has a fish pecked at the body of the fish damaging the surrounding skin.

 

[Katty]

The neons are not kept with snails, I can't speak for sure about whether they were in the dealers tanks but I did not notice any snails around when I bought them.
There has not been an ammonia reading since 2+ weeks ago when the tank finished fishless cycling.
I have not seen any fish pecking any of the others.

 

[WILDER]

The only thing to do really is issolate the neon and try a bacterial med.