When I started adding fish and invertebrates to my FOWLR tank (40 b) I added 5 emerald crabs as the clean up crew, the 2 smallest didn’t make it but 2 months sadly but the 3 larger ones have been going strong and living happily, Or so I thought only 3…… as I was doing my afternoon feeding (around 4 o’clock when I get home from work) the crabs tend to come out and snack on some brine shrimp but as I was doing my head count on the tank I counted 4 crabs! I’m not complaining I’m just wondering where this little guy came from! The tanks has Been set up for about 7 month with fish in it.