I think the only way would be to remove the damsel and rearrange your scape to create a new environment then add the other small fish. Wait a few days and add the damsel back but that's it for a 10g tank.I have one Springeri in my little 10 gallon cube. He was added to help with some flatworms that I had early on. I would LOVE to add another fish, but I'm really afraid that he won't let that happen
He isn't aggressive towards any of the snails, hermit crabs and the one golden banded shrimp that is in there. He doesn't attack my hand when I put it in there, but I think another fish would be a different story. So, he lives alone in his little reef kingdom.