So, I introduced an arrow head crab to my 310 gallon tank yesterday. This evening I found him clutching a large and dead sandsifting goby. I tried to free the goby, but he was already dead. Do you think that the arrow head crab killed the goby OR do you think the goby was already dead and he was just trying to get a meal? I don't actually know. I saw both of my sand sifting gobies earlier today and they both seemed fine and were busy as usual. The arrow head crab is quite large and now I'm wondering if the rest of my fish and gobies are going to be safe. Any thoughts, feedback or recommendations? Thanks!!