Missing fish

[seashells]

Hi all<

Picked up a pair gobies over the weekend. They were together in the same tank for a couple weeks at the lfs. The first couple days home they were visible together doing their thing. They built places under this rock. Now one is missing. They were eating well & sleeping under a rock. The remaining goby has covered all the entrances leading under the rock, but disapears at night & in the morning the cave is open brefly then covered again. It now seems to be guarding the rock. Its been 2 days now since we have seen them together. Tank is covered. Any ideas? I have found another entrance under the same rock... but still see only 1 gobie.

Shellie