I've always been told you cannot competely cover an entire tank with glass/ or whatever covers you've got on your tank as no air will escape.. When I bought my previously owned tank they had glass over the top, I have since cut out pieces of quarter inch thick plexy glass to fit into the sections of my tank, with about a 2" gap on the back of two of the three peices to make room for my two aquaclear 110's. Before I purchase an arrowana I want to seal off the small open areas next to my filters. The rectangular sections are about 2" wide by 6" long.. but I'm not sure if I should completely cover those excess areas with extra peices of plexy glass, or possibly some sort of mesh/netting material to let some air escape.. what do you guys recommend?