I think that each one has different personalities or behaviors. I have a pair of firefish that I bought from the same tank at the pet store. One comes out several times a day, especially during feeding time. The other one never comes out. I panicked the first couple of weeks thinking it was dead, but everytime I moved my rock, there it was! He or she is just happy to hide all day.
1 40 gallon hexagon C.A. cichlid tank
1 10 gallon nano saltwater tank