I can't figure out what is killing my fish. I have noticed that some of my fish before they died, one of the emarld crabs was following it trying to nip at its tail and it had gotten the tail a couple of times. Of course when the fish died, they attack it and ate it. I am grasping here to figure out what is going on. I have other things in there live shrimp, starfish, crabs, anemones, that are doing great. I have liver rock that is growing beautiful purple and green algae. I am at a loss. My Ph is normal, 0 nitrites, nitrates 40 (I am working on that), ammonia 0, sg 1.023-1.024. Any ideas?