I put a male/female pair of emeralds in the tank about 2 months ago to take care of a couple of bubbles. They did a great job, no bubbles since a week after they arrived. One stays out most of the time, the other one hasn't been seen since arrival.
The last time I had emeralds, the male went into the rock at about 1", stayed a couple of months. Came out as Bruce Banner, about 3" tip to tip.