Weird Clicking Sound From My Fishtank

[bristlenoseitplecoman]

Last night I was almost asleep when I heard a weird clicking noise. I thought it came from the living room so I checked it out and went back to bed. a few minutes later I heard it again and realized it was in my fishtank. I turned on my flashlight and looked in but I couldn't see any suspicous behavior. I kept waiting for the click for an hour and then right after it clicked I would turn the flashlight on and look around. Is it my fish? I know it is not the filter or equipment. I own emerald cory catfish (brochis splendens), a BN pleco, a snail, and some black neon tetras that I got a few days ago. Does anyone have any idea what did it? The clicks were short and only went on for one or two seconds.

 

[snake007]

Sometimes the pleco or the cory will come to the top to gulp air, it could be the fish hitting the water surface?

 

[bristlenoseitplecoman]

I did see my cory cat next to the surface so it might of been him.