So I set up my tank a little over 3 months ago after moving back home from college where I had kept my original 5.5 gal SW tank with no issues. The tank I have set up right now is really old and has been dry for 3 years while I was at school (don't know if that's pertinent information or not) It was originally a freshwater tank so I bought some instant ocean salt, got a marine filter and a new submersible heater and a maxi-jet 900 powerhead, I also have two air stones going in it right now and the under gravel filtration left over from the fresh water setup. The first fish I got (forceps butterfly fish and a saddleback puffer) after letting the tank sit for a week or so died after about a week or two in the tank, levels all read zero, pH was 8.4 temp was 78 (which it still is) tried a couple of chromis about a month after I lost my fire shrimp (Nitrite was high when I lost the shrimp) which didn't last but about two weeks either. As of right now I have a lightfoot crab, a blue damsel and about 10 hermit crabs living in the 55 gallon tank and I just lost my newest addition after I did my biweekly 20% water change yesterday, (ammonia was at .25ppm before the change). Currently my levels are NH3/NH4: 0-.25ppm NO2: 0ppm NO3: 0-5ppm pH:8.0 temp 78 degrees Fahrenheit Salinity 1.022.I just ordered a protein skimmer and everybody in the tank right now is healthy and eating fine. I am feeding micro veggie pellets and brine shrimp once a day, I use tap water and instant ocean salt for my water. I am on a well so the water doesn't have chlorine or ammonia in it or anything, the only thing the well water tests out for is iron, manganese and calcium. So can anybody give me pointers? Am I not acclimating right? something to do with my water changes? is my tank cycling again? I'm feeling pretty defeated but I love marine life and the hobby and I really enjoyed my tank I had in college and want to continue having a tank here but I don't want to keep killing fish.