Keeping your own salt water fish tank is an enjoyable hobby which can provide a beautiful centrepiece in a room. In order to ensure proper care for the fish inside, a salt water fish tank requires light on the fish to keep the tank warm, which prevents the use of standard plastic lids. A mesh screen top for the tank provides a cover to prevent fish from jumping out of the tank while also serving to allow the heat lamp to work.
Measure the interior dimensions of the fish tank. An ideal screen will rest inside the top rim, sitting on the lip of the tank.
Subtract twice the width of the framing from the length and width measured. The frame pieces connect with corner pieces which means each side of the frame contains a corner piece at each end that shortens its required length by the width of the framing. For example, on a fish tank that is 90 cm by 60 cm (36 inches by 24 inches) and using 1.2 cm (1/2 inch) wide framing, the 1.2 cm (1/2 inch) width would be multiplied by two to yield 2.5 cm (1 inch), which is then subtracted from each measurement. The result would be a required length of 87.5 cm (35 inches), and a required width of 57.5 cm (23 inches).
Cut two pieces of frame as long as the length of your tank, minus twice the width of the framing, and two pieces as long as the width of the tank, minus the width of the framing.
Insert a corner piece into both ends of each of the two long pieces of framing.
Connect the two side pieces together using the two short pieces of framing, completing your rectangular frame. Test the frame in the tank to ensure it is the proper size.
Cut a piece of mesh that is approximately 7.5 cm (3 inches) longer and 7.5 cm (3 inches) wider than the frame. Use 6 mm (1/4 inch) mesh if you have fish you feel will slip through 1.2 cm (1/2 inch) mesh, or 1.2 cm (1/2 inch) mesh if you do not have any small fish to contain.
Lay the mesh atop the frame, aligning the grid of the mesh with the right angles of the frame.
Cut four pieces of spline to match the four sides of the frame, and press the spline down into the slot in the frame pieces, securing the mesh in place in the process.
Trim off the excess mesh that extends beyond the spline.