Well, I'm very experienced with aquariums since I've had them my whole life and I just turned 69. I have never seen the crab, dead or alive, since placing him in the aquarium and only count one shrimp on occasion. I ordered more,but the last I checked they weren't shipped yet. Kind of expensive for the results I'm having so far. The aquarium has been setup a month before my first order came and everything was good: water temp, chemical balances, etc. I'll give it one more try with this next set.