they are REALLY hard to keep because if you don't have the food that they eat in your tank, in essence you are killing them through starvation. I had some personally and there is only one real way to know for sure if they are alive or not, dig them out from their burrow and rest them on your substrate, if they start to dig in afterwards then they are alive. It is best to have sand with these guys as this will provide another way to tell if they are alive and that is by their filter sticking out of the sand to get food. Yes they are cool things to keep but also really easy to be killed and potentially harm your system.