Honestly I try to stay away from harsh meds unless it is a last resort or I'm treating for ips. I've been able to cure ich on a fahaka puffer with salt and lower temps. Yes, lower temps. It gives the puffer time to fight off the infection because if it is under 86 degrees or even 90 (depending on the ich strain), you're actually helping the ich reproduce quicker.
So the magic number for me is 1 tbsp per 2 gallons of aquarium salt. That has never failed me with any fish. This is what I use for species I know can handle it. For more sensitive species like catfish or puffers, I use 1 tbsp per 2.5 gallons of aquarium salt, but for longer. That's what I used to cure my fahaka and a redtail catfish. Any lower than that and it isn't effective at all and doesn't do too much tbh. Any higher will do better but you have to be careful your fish can handle it.
What I do now before I buy any fish, is look up and see if they naturally inhabit some brackish waters and come back as a natural migration. If they do, or have been proven to survive in semi brackish waters. I know absolutely they can handle the 1 tbsp per 2 gallons. If not it is a huge risk to take on. But if it's close to dying, might as well try. You can look up and see if amazon puffers naturally inhabit brackish or have the opportunity to migrate through, and if so, I can guarantee you 1 tbsp per 2 gallons cures ich. But if you are already using meds it might be best to stick to that because adding all this at the same time will stress the fish and probably kill it faster than the ich. Anyways, good luck and I hope they do better!
