Help?!?!?!?!?

[GoGoLake]

So I have a 75 gallon tank with 3 fish in it, a Yellow Hawaiian Tang, a Juvenile Emperor Angle, and a Red Tailed Trigger. About a week ago I noticed that the Tang was developing black spots on him. I recognized this to be Black Ich right away. A friend of mine who also has owned his fair share of salt water fish suggested that I just lower the salt in the tank to try and rid the fish of the disease with out having to QT. Well now I'm noticing that the spots and grown in amount and the Tang is also scraping up against the sand and rocks. Also I am now noticing that the Angle is also getting several spots on him. I'm worried that lowering the salt isn't helping, but I don't really have enough QT space to take them all out then let the tank sit. So I thought about just putting Formalin in the regular tank, but my friend said that it would kill everything on the live rock and also we would never be able to get it out of the sand. Keeping in mind that soon I am getting a bigger tank to move the three fish into including my Porcupine Puffer who is currently in QT, I need some ideas. Is there any way to successfully treat the fish while keeping them in the regular tank and not ruining the live rock or sand?????

[thor109]

I would buy a 55 gallon on Craig's list. Use it to qt than resell for same price. What ever you decide I would do it fast.

[theman772]

you can use anything that holds water to qt them a big cooler trashcan etc the treatment can/ will make the rock die off