Hi Lorenzo,
You should understand that the reason why hyposalinity is slow in acting to eliminate Marine Ich is because the hyposalinity actually only affects two stages of the parasite's life cycle. When the parasite is in those two stages, the hyposalinity stresses them -- it doesn't necessarily kill them. So fish might go through a couple of cycles with the parasite before the parasite is stressed into submission.
Another thing you should understand is that when you see the trophont on the fish, it is at the end of its cycle. Humans can only see the trophont when it is engorged or what I like to call 'pregnant.' What this means is that there are likely more trophonts on the fish that you can't see which will become visible to you over the next couple of weeks.
So, within these first couple of weeks, you should begin to see progress with a decrease in the disease appearance. Don't expect anything to get better real soon.
About the best thing you can do during this period is the vacuuming I recommended previously AND making sure they are getting the proper foods, with the proper supplements. See this reference and follow its advice closely:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=785228
Keep moving the salinity towards 11ppt to 12ppt. Use a refractometer to control salinity. Monitor things very closely including water quality and pH. Keep the water quality good and pH stable. Nitrites are bad and must be controlled to below 0.5 ppm. So, it looks like you're doing well for now. What is the ammonia level? That must be kept to zero. Test water frequently and with fresh test kits. Make water changes if you need to, in order to control water quality. The reason you don't use hyposalinity in a display tank is because all the small organisms, pods, worms, etc. will die and creat a lot of pollution. So, you are trying to cure your fish in less-than-optimum conditions to begin with. I'm sorry I can't be more possitive about your likely success.
Make sure there is proper/optimum gas exchange going on. The surface of the water needs to be disturbed by a pump flow, for instance. The tank the room is in must have fresh air to avoid a build up of carbon dioxide in the room. If it is safe to do so, remove the lids of the aquarium or, if the fish are prone to jumping, at least partially open the aquarium top. This will improve gas exchange but it will also increase evaporation requiring even more attention to keeping the salinity steady.
How long did you put the fish in freshwater? Did you use methylene blue as recommended?
In the meantime, you should do some extra reading about the parasite:
http://www.petsforum.com/personal/trevor-jones/marineich.html
Although the above reference gives approximate stage times, and you have gotten info on times/days the parasite spends in its cycle, remember this: those are just averages. A good example of this is some work published by Dr. Burgess which shows that some Tomonts have been found to hang around for up to 6 weeks before releasing the swimming, infectious stage. This is far from the average of 8 days typically reported.
When you see the last sign of Marine Ich on the fish in treatment go away, you continue the treatment for at least 6 more weeks (I prefer 8). If you see any signs of Marine Ich during that time, start the clock over. You have to have at least 6 weeks of symptom free time before you begin to slowly raise the salinity. It should take about a week to raise the salinity to 'normal.' After it is raised, you still observe the fish for another 4 or more weeks to verify the treatment was a success.
It is a slow process that requires patience and yet a lot of diligence on the aquarist's part. It gets old quickly, caring for the water quality, vacuuming, etc., but the aquarist that doesn't fail and remains steady is the most likely to succeed.
I don't know how readily available medications are to you, but I would go ahead and order some Cupramine and the Seachem Copper test kit. Just to have those on hand in case you need them. But, Cupramine can only be used in a hospital tank without rocks or carbonate-based substrate.
Other than making sure you performed a proper freshwater dip/bath, I think that is about all I can say at this time. There is always a chance that you caught the disease too late to help the fish, or that it has progressed too quickly because the fish were not in better health.
You can always perform another freshwater dip, but that is up to you. The dip itself is stressful to the fish. Still, doing it to a fish likely to die is better than doing nothing.
Good luck!
Don't hesitate to ask any questions or for more help! :rollface:
