We have a 180g DT , 250g total system. Also have a 55g set up for observation. Two weeks ago we got our first livestock. 2 clowns, 2 Bengai Cardinals, 1 Foxface, 1 lawnmower Blenny and two Skunk Shrimp. We had the fish in the 55g until Monday and decided they were fine to put in the DT. Everyone seemed much happier in the larger tank with more hiding places. Salinity 1.025. Ammonia 0, Nitrate 30, Temp 77.5. This morning one of the Cardinals is dead. No signs of disease or anything. We had noticed one of the Cardinals seemed to like getting right up to the Foxface that is about 2 thirds bigger. Could it have been stung and would it be enough to kill it ? They really are tiny. I'm getting ready to do a water change as a precaution . Thanks