Does it look like the bump at the base of Sully's tail here??? If so, then that's just his caudal peduncle, it's basically just the place where the tail joines the body and it forms a little muscular bump. Sully's isn't very prominent, so it's a bit hard to see XP I'm glad that he's doing a bit better today =D what size tank are you keeping him in and what's your water change schedule like??
I see it, it's just like that, but a bit more prominent. Uhh.. I only got him Wednesday, and haven't done any water changes yet, hes in a five gallon tank, filtered, heated, staying consistently at 81F
Suggestions on water change schedule?
Some of them have more prominent peduncles than others, it shouldn't be anything to worry about =D Sounds like he has a great set up!!!! In a five gallon tank, I think 50 to 75% with a gravel siphon would be appropriate =)
You should clean the gravel once a week, but you shouldn't have to do any 100% changes in a 5 gallon unless the fish gets really sick. 5 gallon tanks are big enough that beneficial bacteria will build up over time, and 100% water changes will just get rid of all that good bacteria.
if you're nervous about sucking him up in the syphon, then yes that might be a good idea =) just make sure you float him in his cup in the tank before re-introducing him so that he doesn't get temperature shock.