Diamond Tetra Trouble

[nadajdui]

Hey all. Well, I just noticed about a week ago that one of my 7 diamond tetras has a dark spot on her side. None of the others have this, not even after feeding, and it wasn't there when I bought her. I got them all as a group. She is not showing any abnormal behavior, and is always out and about and eating well. Tank stats are as follows:

Tank: 33 Gallons (36"L 18"T 12"W)
Ph:6.8-7
Ammonia:0
Nitrites:0
Nitrates:5-10
Plants: Medium planted
Lighting: 64 (I THINK) watts
Livestock: 7 diamond tetras, 1 male full grown BN Pleco
Chemicals: Leaf Zone
Anything Added in the last week or so: No

Here's a picture of the diamond tetra in question:

 

[WILDER]

Is it defiantely a spot not a patch, as black patches can be ammonia burns that are healing, there is a parasite like black spot, and also black patches can be number of things even cancer.

 

[nadajdui]

Thanks, Wilder.
Do you have any suggestions on how to deal with it, or if I ever can at all?

 

[WILDER]

Not sure what it is to be honest.
Is it a spot or patch hard to tell in the pic.

 

[nadajdui]

It looks like it's inside of her, not on the outside. Sorry, should have said that before. But it's not getting any better, or any worse. She's still acting fine and eating.

 

[WILDER]

Can you issolate her as I would try a bacterial med, if it's on the inside don't no what it is.
But a bacterial med is your best shot at the moment, if its a cancer sorry the med won't help though.

 

[nadajdui]

All right, thanks.