I have a 25g nano cube that has been running for several years. I have two very healthy and active fish in it (a clown fish and a tang). For the first few months after it cycled I was able to keep corals and anemones but for the past couple years any coral or anemone I buy dies withing 24 hours of going in to the tank. My ammonia and nitrates have always tested fine. I buy ocean water from petco. My salinity tested a bit hight but I don't think it's high enough to cause death that quickly. Even the snails I bought yesterday are already dead. Any suggestion on what else I can test for? I would really like to add to my tank but I don't want to keep throwing away money for anemones and corals that die 24 hours later. Why would my fish be so healthy but corals die that quickly?