Sounds normal for them to me. When I set up my 1st tank some years back I was told to purchase 6 damsels to cycle my 55g (eeek) and 3 lived... 2 green chromis, 1 blue ... this fish was as bold as they come. I often thought he had gone mental from the cycle because he was so aggressive he would attack the glass when I walked by and I knew he would nip me each time I reached in to clean the tank with out fail until my arm was out of the tank. S/he claimed the entire 2/3 left side of the tank and there was no bending on that. S/he dug as you mentioned as well.
I hated to part with anything I had so I tried adding my fish, a kole tang, a royal gramma and a clown and he was not very nice to the new additions so I trapped him and took him to the LFS
. Be very careful before adding any new fish.