It sounds like you want glass tops like BillD said. That would be pretty easy. measure the diameter of the lip around the top of the tank, the inside of the plastic rim, assuming you have standard glass tanks. Decide on the size of your top, leaving room for gas exchange and filter connections. Cut 2 pieces of glass, one to be the lid, the other to be the "door". glue a "knob" on top of the "door" so it can be easily lifted. You can try and find a way to hinge the two pieces together, or just have the "door" a "lift and remove" piece.