I know corys will surface for air every now and then,but i have a couple that will hang out on the surface for minutes at a time. It is only a couple of them out of 13 in the tank,so I think its the same two. Params are 0-0-<20 so I know its not a water issue. All the fish seem very healthy and active and I dont think its a problem,but I was just wondering if anybody else had corys that "hang out" at the surface. 30 gallon tank over filtered by Aqua-Tech 30-60 and a 20-40.