I woke up this morning to find one of my Zebra Danios dried up on the floor.

I immediatly checked out my tank, nothing was different(except for a missing Danio). I have had the same setup for about 6 months, with no problems at all. I only have one very small opening in front of the filter. I can't even close that up any more than it is, or the water exitting the filter won't be enter the tank.