It probably depends on how big they are, but they can be sexed. My understanding is that the males have a red band on the bottom of their anal fin where the female's is solid yellow. (LFS told me this, so I'm not 100% positive.)
It took mine a couple weeks to get used to the tank to the point she'd come out at feeding time. She's been in about a month and a half now and she's just starting to show herself on a regular basis ('bout the same size as yours w/ similar tank mates.)
I wouldn't buy another or get a shrimp just yet. The shrimp could, in fact, make viewing the fish more difficult if it picks a spot in the back of the tank. Depending on what you're planning for the tank, pistol's can be a potential nuisance as well. (Signal gobies do not
have to be paired w/ a shrimp.)
I have mine in the tank with a Yellow Nose Signal about half the Yashia's size. As of this morning, the two are sharing the Yellow Nose's cave right in the front of the tank
.
