Beginner with a 13.5g Fluval all in one Nano reef tank about 1 month in. At the turn back now and forget it stage. Set up the tank and tested the water at my fish store all ok. Lost a clown fish day 3....couple weeks later lost a chromie....yesterday trying 2 tiny blue and red leg hermit crabs and today the 1 isn't moving and can't find the other. We cannot figure out what is going on. Any ideas before I unplug it all? I just wanted a nice small tank with a couple fish and a few corals to look at. Thanks.