I just bought a 120g tank complete. My sister is very familiar with saltwater tanks and has a 75 g reef tank. I am new to all of this. She bought a 180 g complete from the same individual. We went to the home, drained the water removed the fish, live rock and live sand. Traveling home she called her contact in Louisville, KY to ask about reusing the live sand. He said absolutely not. He said it would release extreme nitrates and ammonia. She called 4 other aquarium stores and they told her it was no problem to use the sand if it was kept moist. We transported the water, set the tank up, put in the sand, rock and water. Everything looked great day one, yesterday the fish weren't doing well. (Sailfin, yellow tang, 2 maroon clowns, a Sally lightfoot? and 3 blennies, I think). Had one individual tell me I didn't need a protein skimmer if this was all of the fish I had in the tank. The set up that came with it was ancient. My sisters contact said to get a skimmer ASAP and also a new return pump, so I did. My sister felt the fish were definitely not going to make it so don't worry about it. She can only help over the phone as she is 2 hrs away. I couldn't stand to see the fish die, So I mised up some salt water, drained the tank, removed the live rock so I could catch them and took them out and put them in new salt h20 with a power head and thermometer. The aquarium nitrates/nitrites are off the chart and I am not sure where to go from here. How long can the fish survive in my 55 gal trash can with a powerhead if I keep changing out the h20? How often should I cange the H20? Was this from reusing the live sand or would this have happened anyhow? Also, I wasn't prepared for the relocation and the water that I have used from home is tap h20, which I have read is definitely not good. My sister knew I should use RO, but like I said we weren;t prepared. Any suggestions?