A Cut Near The Gill Of My Albino Rainbow Shark?

[flamie]

Tonight when I checked my tank I found my albino rainbow shark not acting normally.  He/ She is not eating, hiding behind the plants and is not moving much. Usually I see him/ her cruise the tank every now and then. Finally I found out there's something wrong beside his/ her gill. It looks like a inflamed cut or something. Please see the attached picture. Does anyone know what's wrong with it?
 
Tank info:
 
90 Gallon, lots of plants, water parameters good, no ammonia/ nitrite, nitrate ~20.
 
Tankmates: a couple of rainbow fishes, denison barbs, zebra danios, pleco, corycats, peal gourami, and a male betta. All in all, nobody can really beat him up. He/ she is about 3~4 inches long, and is the boss/ biggest in the tank. I have kept him/ her for half a year and he/ she's been very healthy, growing stronger but rarely bothered his/ her tankmates. 
 
Could anyone help me out? I don't know what kind of disease this is. I currently moved it from the main tank to a hospital tank. I've added salt, stress guard, melafix, and pimafix in the water. That's all that I can think of. If you come up with any idea let me know.

 

[the_lock_man]

It looks more like a physical cut to me, is there anything in the tank that the fish could have hurt itself on?
 
PS, Off topic, I know, but the gourami and the betta will probably end up fighting each other, they are both territorial surface-dwelling fish, unless you have plenty of tall plants in there so they aren't constantly looking at each other. Even then, it's a big risk.

 

[star4]

Does your heater have a cover? if not it maybe a heater burn. Melafix and primafix should sort this out, however if the fish is not eating try soaking its food in a drop of garlic juice. (add a small amount of food to a pot with water and add a drop of garlic juice and leave it for an hour).

 

[flamie]

It looks more like a physical cut to me, is there anything in the tank that the fish could have hurt itself on?
 
PS, Off topic, I know, but the gourami and the betta will probably end up fighting each other, they are both territorial surface-dwelling fish, unless you have plenty of tall plants in there so they aren't constantly looking at each other. Even then, it's a big risk.

Thanks for the reply. I was thinking of the same thing. It might be the shell that I put in a couple of days ago for decoration. I have taken it out in case other fish gets hurt.

My betta is a double half moon. He's quite cool, never bothered anyone. I have a heavily planted tank, with a lot of covering plants providing shade. I never saw him and gourami fight each other.

Does your heater have a cover? if not it maybe a heater burn. Melafix and primafix should sort this out, however if the fish is not eating try soaking its food in a drop of garlic juice. (add a small amount of food to a pot with water and add a drop of garlic juice and leave it for an hour).

I don't have the heater in place since it's summer time. He looks ok today, but still wouldn't touch the food. How does the garlic thing work? Do I just pound the garlic?