I have been wondering at the bald spots at the bottom of my tank for awhile now... areas where the sand is pushed away and the glass bottom is bare. As the spots were occurring in high traffic areas where the fish tend to take rapid turns while weaving through the coral, I figured it was just being "blown" around by the repeated movement.
However I was watching my tank this evening and my clown settled in one of these cleared spots and shook, throwing up a cloud of sand and furthering the bald spot. He (I don't know for sure if it is male or female) didn't touch the bottom or any of the rocks, and he quickly moved out of the resulting sand storm. It was like he wanted that spot free of sand for some reason.
Any ideas what is going on here? It seems healthy, though I have witnessed him nipping a chocolate tang that is in the tank with him. He leaves the Coral Beauty and yellow tang alone. Is he bizarre, or does he just like being able to watch the Chaeto grow in the fuge below?
The tank is a 65 with 10 gallon fuge, water quality good (0 A, 0 Ni, 5 Na, 8.2 pH, 79 deg, 1.021 sal), above mentioned fish with colony of green button polyps added 1 week ago. All doing/eating fine.