Young peppered longfin acting odd

Picture below - I believe it's a peppered longfin?
Anyway, we've been fighting a battle to get him back to normal, as the lil guy is sometimes on his side, but today I noticed he struggled a bit to swim, finally mustered the energy to snatch air from the surface and came down to the bottom a little hard and crash landed. He didn't seem hurt by it, but it was weird that he sunk a bit out of control. I know swim bladder disease causes corys do swim all funky, but they usually can't stop floating when that happens. This seems to be the opposite?

 

His tailfin looks a little beat up, has he been picked on by other fish in the tank that you know of?

 

His tailfin looks a little beat up, has he been picked on by other fish in the tank that you know of?

Definitely not, only two other fish are an older peppered cory (who sadly passed away today, seems like a swim bladder disease issue), and another youung cory that is so skittish I only see it when the tank lights are off.

 

I'm sorry for your loss. If one fish in the same tank had swim bladder problems I wouldn't be surprised if the other one is suffering the same thing. There are multiple things that can cause swim bladder issues, one is poor diet. What do you feed your cories?

 

I'm sorry for your loss. If one fish in the same tank had swim bladder problems I wouldn't be surprised if the other one is suffering the same thing. There are multiple things that can cause swim bladder issues, one is poor diet. What do you feed your cories?

Thank you, 11+ years no issues with that cory. new corys added late November, 2 died within a month, this longfin this topic is about in questionable condition, and a panda cory that looks totally fine. The pand corys species buddy was one of the first to die of this batch.

Feeding them Hikari sinking wafers, recently switched from the hikari algae wafers to try to avail this guy's issue. I boiled some peas last night and unshelled and mashed them and put them in the water to see if that will help with swim bladder issues.

Water parameters look fine, but I'm waiting for my api master kit to arrive today, as I'm out of ammonia testing solution and the api test strips don't test ammonia, oddly enough.

 

This guy is a longfin bronze cory. I've kept a couple of these guys before and they don't seem to be as hardy as the normal-fin variety. I think both eventually succumbed to this sort of swim bladder disorder. It could be a genetic susceptibility attached to the genes responsible for producing the longfin effect, or via a founder effect. Or they may just have weaker immune systems due to inbreeding. I think I talked about how to possibly remedy this problem, if it's treatable, in your other thread.