The costs of putting together an aquarium, with all the accessories and the fish, add up fast. Don't consider forgoing the hood. It's one piece you shouldn't leave out, as it will reduce water evaporation, keep enthusiastic fish from jumping out of the tank and will keep things, not excluding cats, from getting in. Consider making the aquarium hood yourself instead of purchasing it.
Aquarium and Hood Measurements
Before you can make an aquarium hood, you need to know the measurements of your aquarium. Take a tape measure to the top of your aquarium, measure accurately, and write down the length and width. The hood will need to slide down over the edges of the top of your aquarium, so add a quarter-inch to both measurements to make the hood just a bit larger than the top of the tank.
Materials You Can Use
Wood might be the first thing you think of to build your aquarium hood. While pine and plywood are common and useful for making hoods for fish tanks, you can actually make your aquarium hood from almost anything, including metal roofing material, PVC or even rain gutters. Also gather other items such as screws, hinges, a drill, a saw and glue -- wood glue if you're using wood and acrylic cement or PVC pipe glue if you're using a plastic material. If you're building a wooden hood, you'll want to paint the exterior the color of your choice, but you'll need the inside of the top of the hood to be reflective to maximize the amount of light inside the tank. This will enhance visibility when you're looking in and will benefit live plants in your tank. You can always apply mirror reflectors, but white water-resistant paint is easier to apply and is reflective enough to serve the purpose.
Light It Up
Many commercial aquarium hoods hold aquarium lights that allow you to illuminate the inside of your tank. Just because your hood is DIY, that doesn't mean you can't have lights, too. You'll have to attach locking and non-locking clips to the inside of the top of your hood to hold the bulbs in place. You should also get two pre-wired waterproof end caps for each bulb. These can be purchased at your fish or aquarium supply store.
Make a Glass Top
If you want to give your DIY aquarium hood a unique look, consider giving it a glass top with lightweight glass panels that slide to allow you easy access to the interior of your tank. You'll build a basic frame for the hood, but you won't attach a PVC or wooden top with hinges. Instead, you'll build a nonmovable piece on the back one-third to one-half of the hood. You'll insert a piece of glass in the front two-thirds of the top using strips of PVC -- one that has double grooves -- attached to each side of the hood to allow your glass top to slide open and closed easily. Glue a handle onto the top of the glass piece so you have something to grasp when you open and close your sliding glass lid. If your aquarium is large, install two smaller panels instead of one large panel.