Does anyone here have any experience with these little guys. i rescued 4 of them from wal mart and i was taking care of them and then i saw that one died. i did notice that they werent eating the shrimp i was giving to them. what should i feed them? and do they dig tunnels? i think the sand might be too fine and is collapsing on them... should i cut some clear siphon tubing and make tunnels for them? how do i take care of them?