New tank bought on craigslist

ok so my naso isn't dead but is very stressed to the point it wont move. it was behind the rocks and if i turned power heads off it would get pushed back and forth and never try and fight it not even a fin flip so i moved some rocks so i could get it out of the tank and then it moved but went to another cave where i can just one of its eyes but still wont move. im very worried that it is going to die if i cant figure out what is stressing her out. tank parameters are temp 78, ammonia 0ppm, nitrites 0ppm, nitrates 5ppm, ph 7.8 before the lights came on. any ideas????????
Stress from being introduced to a new system can sometimes be enough to do it. You should set up a QT tank and monitor new fish. It's easy to treat anything they come in with, and keep an eye on them since the tank will more then likely be bare (I'd add some pieces of PVC for swim-throughs/caves though). Also, what are you feeding the fish? Have you tried soaking the food in garlic and vitamins? This way, their immune system will get a nice little boost and should help them fight off stuff naturally. I have a Hippo tang that I've had since it was about 1-1.5" and is now almost 4". It's survived Ich, Marine Velvet, some type of Fungal Infection, and god knows what else with no type of treatment other then enriched food and tons of algae covered rocks to pick at. Sorry to hear about your losses. Hope things pick up for you!
It may be new but it was set up with everything from my 55 everything was taken our of my 55 and went straight to my QT tank and after the 150 was filled everything went in the 150 and was never in the air but to go from tank to bucket and back to tank I have spa lps leather and soft coral and everything is happy healthy and eating and there has not been any kind of mini cycle at all there was 83 lbs of rock from my 55 and the sand was washed before being put in the one fifty and this happens overnight up until yesterday it was swimming AMD picking at the rocks but would not touch the algae strips or mysis or brine shrimp witch was soaked with garlic the yellow tang and coral beauty where added at the same time and both are doing very well the yellow tang is getting fat he was a bit on the thin side when I got him