I have had a pair of clownfish since July. They're my first fish as the tank has been operational since about May. The entire time I've had them they live at the surface in one area, pretty much. I turned off my return pump and powerheads today for a bit to try spot feeding my corals and this was the first time they ventured below the top. They made it about halfway down my 120gal tank and returned to the surface when the pumps went back on. Is this normal?