They do best if kept with more then 1. I have had several of them and at one time I had 4 in my 20 gal
fuge. I bought a small yellow shrimp goby and he killed them all over time. I could never catch the goby.... They are a cool fish. I crushed up shells and put that in with them so they could use the pieces to make there homes. They even had a door that they would close at night. I will be getting some more soon... I have not seen that goby in months... I think when i was moving the LR
around I pinned him in somewhere...
The fish that was gone in a day was either acclimation or the star would be my guess..... If you want them i would get rid of the star....JMO