I went on to nutrafin web site, not there to download. Is the master test kit definately suitable for saltwater??
Can you get samples tested tommorrow and get the lfs to write the results down for you so that you have figures. Insist on this. The two tests it shows on website under products both use the same number chart you see, am really wondering why you divide by 1.22. Most other test kits are done in 3-5 mins aswell, even my 2 part F/W Nutrafin ammonia test.
Keep an eye on the fish, only reason I say this is that Tangs are susceptible to white spot and white spot tends to bcome apparent when water conditions are not good. That flicking on the rocks is a tell tale sign. Be very vigilant and watch like a hawk to see if you get any salty grain spots appear, look at fins first, they seem to go there first.
Can you tell us exactly what inverts you have aswell, if white spot does break out, there are certain meds to be avoided. Face that if it happens.