I have a hi fin goby and candy cane pistol shrimp. I added them a week apart, with the goby being first. I made a little cave with my finger under a rock and he lived there for the week. I then added the shrimp and put him directly over the same cave opening and he went right in. They moved homes and went under my larger rocks but have been together ever since. When my goby comes out, he stays right near the cave opening and I only see the shrimp occasionally.