I don't know what to do I called a local store and he said I could try a fresh water dip but it's probably too late to do anything. So all I have done for now is I added a some methlene blue to hopefully help him breath a little easier for now.
My hands are tied by not having seen what you've seen.
Sorry for the loss.
If a water change is done properly, it can only help, never harm the fish. You'll need to listen to your LFS with a lot of skepticism.
I'm unsure what is in the buffer control you used, so I can't support its use. Keep in mind that those water controls were meant to be used in salt water of relatively normal sp. gr. and not during a hyposalinity treatment. Some are not suitable as pH adjusters since they are in fact 'buffering compounds' rather than just pH adjusters.
I think you're okay in attempting another fish. Just don't alter any treatment procedure or process. Time was lost with a mis-treatment. Had you confirmed it didn't work, we might have gone on the assumption it wasn't Marine Ich. Still. . .hard to say.
Don't be discouraged. Before the next fish do a thorough cleaning of the QT and QT equipment AND let it dry out completely for at least 48 hours before you use it again. Regarding cleaning, you should read this: Cleaning Procedures. Please remember not to change the instructions but to follow them closely.
Also, to be on the conservative side, read this link and actually print it out to use it when choosing your next fish: Should I buy that fish?.
If the one fish did have Marine Ich, then all the fish are to be considered infected. A low level infection of Marine Ich can remain well hidden from the unaided human eye.
There are two approaches to this. One is very stressful to the fishes and that is to do nothing about the fish already there. Quarantine all new fish to be sure they are not infected. However, when the new,healthy fish goes into the DT there is a chance the parasite will bloom into a much larger infection, possibly killing some of the fish that were already there (as well as the new addition).
The above cycle will continue for about a year. However, you could just stop adding fish for a whole year and that will pretty much make the Marine Ich lose its efficacy. We found that Marine Ich will pretty much become benign after about 10-12 months. BUT there must be no new Marine Ich introduced during that time. After that year, it is safe again to add fish that have been quarantined. Only now there would not be an outbreak of disease.
The other alternative is to take out all the fish, treat them, let the tank go fallow for 8 weeks (no fish), then return the fish to the tank when they are cured and the tank is ready.
Keep in mind that fish are not 'happy' nor sad. Their health is determined by skin scrapings, fin clips, gill clips, feces examination, as well as visual evidence. We are not likely able to tell a healthy fish just by looking at it, yet we can go by some visual clues. What we do know is that from visual signs, we know the fish has a problem. We just can't say the opposite.
