last night i heard gravel moving around so i turned on the light to my aquarium and my 2 socolofi were backing into each other so that their anal fins were touching (this was taking place in a little hole in the gravel that they seemed to have dug) but when when they noticed the light was on their scattered, but later that night i heard the same noise, but this time instead of turning on the light i just left them alone. is this normal behavior for a male/female pair?