help! weird pimple on my cory

[son2fu]

1~What type of fish is afflicted? In addition, please describe what is wrong with the fish to the best of your ability (i.e. cotton like growth, bloated, etc.).
my Bronze cory( corydoras aeneus i think) it has a red pimple like structure growing on the base of its arm fin.
2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)? Please give exact values.
ammonia-0 nitrite-0 nitrate- about 7 pH- 6.6
3~ How large is the tank? How long has the tank been set up?
the tank is a 26 gallon, its been set up since december.
4~What type of filtration are you using? Please give the name and number (i.e. Fluval 304) and amount of gph if known.
marineland Penguin biowheel 200(gph) rate for 50 gal.
5~How many fish are in the tank? What kinds of fish are they and what are their current sizes?
i have a dragon goby, 6 tiger barbs and 5 other bronze cory's, along with the sick one.
6~When is the last time you did a water change and vacuum the gravel? How often do you do this? How much water do you remove at a time?
5 days ago, everyweek, 10 percent
7~How long have you had the fish? If the fish is new, how did you acclimate it/them?
i've had this fish fora bout 3 weeks i acclimated it in the bag for an hour and put it in the tank.
8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.?
no
9~What kind of food have you been feeding your fish, have you changed their diet recently?
i feed spirulina discs and bloodworms frozen i just started feeding the worms


picture

http://i127.photobucket.com/albums/p128/syssardsipper/sickcory1.jpg

 

[son2fu]

does anyone know?

 

[Zagz]

What kind of tests are you using? It is unusual to have a tank with no nitrates that has been set up for 3 months. Is he acting different, not eating? Lethargic at all, breathing fast? I'm not seeing what you are talking about in the picture to be honest. I may just be blind. I would do 25% pwc per week.

Has the spot grown at all? Does he flash against anything?

 

[Devilishturtles]

Sometimes, things like that just pop up and you don't know why. It can be from, literally...anything. How long have you noticed it? Does it seem to be open or infected, or just there? I would maybe treat with a dose of melafix and pimafix and keep and eye on it. If it stays benign like it is, I wouldn't worry about it.

 

[son2fu]

What kind of tests are you using? It is unusual to have a tank with no nitrates that has been set up for 3 months. Is he acting different, not eating? Lethargic at all, breathing fast? I'm not seeing what you are talking about in the picture to be honest. I may just be blind. I would do 25% pwc per week.

Has the spot grown at all? Does he flash against anything?

the tests like i said before indicate 7ppm of nitrate. he's not acting any differently, he's breathing normal, in the picture, its a red blotch on his left fin, the swimming one. what is lethargic and what do you mean by flashing? he exerts normal behavior.
i went down to the lfs yesterday and the man told me taht it might just be a tumor, it hasnt grown, in fact, it shrunk(like apimple would).

 

[Zagz]

Flashing is when they rub against items in the tank. Are the tests strips or liquid? It may very well be a tumor.

 

[son2fu]

liquid, AP fresh kit.