Yes, the lump looks just like a lump. There does not seem to be anything around it. The inside of the gills seem to look ok. It does seem like the gill seems folded up or bent forward persay. Also so does the other gill with out the lump. This bump just appeared within the last week. A closer look at it seems that it is attached to the inside of the gill, but when it breaths it looks like it may have grown around in a shape that allows to somewhat close shut. If that is understandable. Water and other fish are all ok. I have had fish with tumors before so I do not want to treat the tank if it is a tumor. I have not seen this before in any fish I have ever had.
What size tank is this? What are you water parameters (ammonia, nitrite, nitrate)? Is this fish or any of his tankmates new? My first guess would be a parasite but it would have to have originated from somewhere (either a new unquaratined fish or this fish being new). Some more info will help!
Water is all good. It is a 80 gal tank that has been established for 3 yrs. 4 fish in it. 2 silver dollars and 2 goldfish. Temp running 72-74. No new fish, I had a pleco die about a month ago but do not know why. Died sudden not warning
Hmm...very odd. Its def not a parasite without the introduction of new fish. Have you tried to touch this with a q-tip to see if its hard or sticky or fuzzy? If its hard, then a tumor is the most likely answer & theres little that can be done (exception being surgical removal). If he doesnt seem to be in any distress, i would just let things be until he tells you otherwise.