Bangaii Card..Question

[geopod]

Lately I noticed that the Bangaii's I have only come out of a corner one at a time. One always stays in the corner and the other one feeds and comes back to the hole and then the other one goes and feeds.They have been doing this for about 5 days now....Any idea for those of you that have Bangaii Cards in their tanks.
They are acting like they are protecting the corner.i cant see anything cause the way the rock is.

george