I figured that the fish had fungus, so I went out and bought a treatment (the only one in the store). It is basically just a fizzing tablet, and I added three (as per instructions, and based on the capacity of my tank). They fizzed away immediately, but also turned my water green, which the box didn't say anything about!
Anyways, judging from these (bad, because of the green water) pics, can anyone tell me if this fish really has fungus? I greatly appreciate it.
Water parameters:
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: 10 ppm
pH: 8.1
I'm not sure of the exact measurement of my water's hardness, but I do know that it is somewhat soft.



The lump is at the base of the caudal (tail) fin, on the top.