The Puffer Forum

Thanks for the great shot. He definitely has some sort of a severe infection in his mouth. I'd start by getting a good liquid test kit & check his water. Then do a 50% WC today & tomorrow. Add 1 tbsp salt/10g & Melafix I Pimafix to the water. Be sure to replace these, after you do the WC.

OK. Have followed all advice. Including switching to Prime. After first day of 50% water change he seemed rejuvenated enough that I actually tried feeding him. No dice. He ignored it. Much more swimming instead of laying on the substrate though. Mouth still a weird texture, but not as puffy looking.
Did another 50% change yesterday + salt, melafix and pimafix. He immediately seemed really stressed: laying on the bottom & very dark in color. His back looking mottled instead of stripey.
Tested nitrates a moment ago. They are ~ 5 ppm.
So, where do I go from here? Do I do a 7 day course of treatment, as is recommended on the Mela/Pima fix bottles, or are puffers delicate enough that I need to ease off? He has been swimming around today, but then when he stops to rest on the substrate he gets all dark & blotchy again.

I wouldn't worry to much about feeding him at the moment since he isn't feeling well. What may have caused the stress was that pimafix and melafix cause the dissolved oxygen level inside the water to drop, if you can add in an airstone for him it'll probably help. Continue on in the treatment until the spot looks normal and healthy.

Whilst sitting still they try to blend in, this is probably the change of colour you are seeing

Update:
He is doing fine! After more a week of treatment & several water changes, he still wasn't eating & appeared to be wasting away. My husband & I were ready to euthanize, because I could not bear watching him starve to death.
As a last resort, before taking the final step, my husband hand fed him - basically shoving the shrimp into his mouth. It energized Sriracha, and he's been going strong and eating on his own ever since.

It was recommended that I mix up his diet a bit, and to that end I picked up some live foods at Petsmart today. Some snails that need to quarantine for a bit, but I also got superworms. I'm embarrassed to admit that I thought this was just a fancy sales name for night crawlers, but it's giant meal worms. If my husband or I can bring ourselves to touch them, is this OK to feed?

Also, they had some little live crabs at a reasonable price for food, BUT I would not be able to rip off their little claws. Hubby says the guy in his fish club who has a fahaka takes off claws before feeding live foods to prevent injuries. Is this really necessary? The claws on these guys were teeny....

Thanks for your help!

That's great news. I never remove the claws, no crabs really hurt him but they have pinched

Careful with those Superworms. They are extremely fatty (probably a good thing, considering he was starving) but their outer shell (chiton), is difficult for them to digest. They do have those nice big Canadian night crawlers at Walmart.