I found a 35 gal aquarium that was in good shape and it was sitting in the sidewalk. I picked it up and decided I'd start a salwater aquarium and make it into a coral reef of my dreams. I bought everything i needed for it: live reef sand, decoration white sand, hydrometer, thermonmeter, surface skimmer, 6 watt led lighting, two filter, filter cartlidges, activated carbon, nitrite test kit, xp filter, pump, submersilbe lighting, dead rock, decoration tree coral, and quickstart. Boy, was I wrong. That was two months ago. Since then I have spent over $300+ just on trying to get the aquarium started. After the first month of letting the tank cycle, I first bought a tester fish to see how he survived in my tank. It was a blue damsel yellow tail, he died the next day. I then went to the fish store and they tested my water and it was high in ammonia. So i bought more quickstart and after several weeks of contiunous testing and adding quckstart to my tank it was still high in nirite. I then did dramatic water changes with the pre made saltwater from the local fish store. Finally I bought two blue devil damsel fish in september and the are still alive. My nitrite level was still high at 1.0. Then for almost two weeks I tested my water and it was at 0 nitrite so I decided to add another fish. I went to the fish store and bought a small yellow tang and a stripes damsel. For a couple days the nitrite was still at 0 and I was happy and thought well this tank may actually become the tank of my dreams. I test my water regurlarly everyday. Then one day the nitrate went off the charts purple testing at 5.0! This hasnt changed. Then 2 days ago I came home to find my yellow tang at the bottom on my tank with his eye poping out and with black around his eyes one of his eyes looked infected with cloudy gooey stuff on it. He was still breathing tho. I then went to the fish store and got some c02 water I belive its called. He instantly reacted a little more lively. But after two hours he was doing bad again, laying on the floor, not moving but still breating. I was heartbroken in watching him be in pain, so I flushed him. I then decided to do a dramatic water change the next day(yesturday). I had the fish store owner come to my home and deliver the water for me. I changed the water I tested it its salinity tester fine at 32 but nitrate is still at 5.0, even though its fresh new saltwater from the store. I believe maybe the sand contaiminated the water. But im not sure what the problem is. Today I came home and I found my stripes damsel dead. But my blue devil damsels are still alive. I have done numerous trips to the fishstore to buy saltwater or quickstart, ammonia remover nurifying bacteria. I do not know what else to do. The fish store workers dont know what the problem is since I have been doing everything im supposed to do but somewhere Ive gone wrong but I dont know where. I hope somebody will be able to tell me by all the details I have provided. Right now when i test my nitrite it tests at 5.0. Please help me. This was supposed to be a hobby but lately it has just become a headache. I have spent so much money just on trying to get it started but noting works. I cant get the nitrite to go down and stay at 0 nitrite. Could it have anything to do because i dont have any live rock in it, or because it doesnt have a cover to stop the evaporation? It evaporates dramaticly each day about a inch of water or so.