Growth on blackfin cory

[lilu]

I've noticed over the last week an odd growth on my blackfin cory's face and also on its dorsal fin. The growth doesn't look like ich, rather it appears to be similar to a 'skin tag'. The growth is not fuzzy or red. No other fish is affected. The tank parameters are:

pH:7.2-7.6 (depending on whether the CO2 is on or not)
ammonia: 0
nitrite: 0
nitrate: ~5ppm
temp: 77-78
phosphate: 0-0.1
Fe:0
chelated Fe:0.1
KH: 80
GH: 260
copper: 0

Tank is a 12G moderately heavily planted tank: valisneria, rotala macandra, amazon sword, Sponogetons crispus, Christmas moss on driftwood, Ludwigia repens. Other inhabitants include: 6 neon tetras, 2 Hasboro cories, 1 Oto, 3 ghost shrimp, 1 yellow shrimp, 1 blue shrimp, 1 cherry shrimp, 2 amano shrimp, several assassin snails (started with 2 to control snail population, now I am removing these snails with each water change and giving them to friends with aquariums because they have completely eliminated the pond and ramshorn snail population).

The blackfin cory doesn't appear to be eating well - I haven't seen it eat for the last 3 days, it spends most of the time sitting on the ludwigia leaves or "treading water" in one spot.

Has anyone seen this type of growth before? Any thoughts to treatment?

Thanks!!

[lilu]

Update - looks the catfish isn't going to make it. Today I found it laying partially on its side not moving and breathing appears to be difficult. It hasn't eaten in a few days.

[plantedtankfan]

You should remove it right away and put it out of its misery. It look like the scales are falling off...

[ValMM]

Corydoras don't have scales.
But if it is not doing well, it may be best to kill it.