Problem with black skit tetra

[Fishmanic]

My black skirt tetra has a black area under his mouth and on the lower side of one of his gills. I treated with levamisole and after another water change I treated with prazipro. He is not eating and is less active but can still swim. Water quality is fine. I dont know what else to try. The other fish in the tank are fine including 2 other black skirt tetra. Any advice is welcome. Pics follow:

 

[Fishmanic]

Oh.... I did add 5 tablespoons of aquarium salt after the last large water change. The tank is a 35 gallon tank.

 

[Naughts]

How are your nitrates?

 

[Fishmanic]

They max out at about 25 after a week and just before water change. My tap us about 5 ppm.

 

[PheonixKingZ]

Does the black look fuzzy? Smooth?

Is there anything sharp in the tank? (Decor, plastic plants, etc.)

 

[Naughts]

OK, they are not high. Environmental nitrates was the only thing I found that would cause black patches. Sorry.

 

[PheonixKingZ]

How are your ammonia readings?

 

[Fishmanic]

it appears smooth....this starting appearing about 8 or 9 days ago. I havent seen him eat since then.

 

[PheonixKingZ]

The only thing I know that causes black patches, are ammonia burns, caused by high ammonia levels. What are your readings?

 

[Fishmanic]

Ammonia is 0.. nitrites 0, Ph 7.5

 

[PheonixKingZ]

Interesting. The only thing I know that causes black discoloring on fish, is ammonia burns.

Reduce feeding for a bit and remove any dead/dying plants and/or uneaten food.

It may just be natural discoloration, but this treatment is just used as a precaution.

 

[Fishmanic]

I have been using mainly frozen foods over the last week to cut down on leftover food as the fish in the tank gobble every bit. I do deep gravel cleaning to lessen rotting plant matter and leftover food.

 

[PheonixKingZ]

If only the one fish has it, I wouldn’t loose sleep about it.

If all the other fish developed these coloration, I would worry.

I think it’s just natural coloration, but keep an eye on him.

 

[Fishmanic]

I dont notice that coloration on any of the other Blackskirt tetra. Also his mouth is opening and closing more than it should. I have plenty of oxygenation in the tank via flow from HOB , an airstone,, and a sponge filter.

 

[PheonixKingZ]

Gasping also indicates ammonia poisoning. I don’t mean to keep nagging, but all the signs are pointing to high ammonia levels.