Most people with an aquarium have some sort of top or canopy to cover it. The most common types are plastic hoods and glass canopies. Plastic hoods do not have enough light to be used on reef aquariums. They also are not clear to allow you to use the high powered lighting that is required. A glass canopy can be used for a reef aquarium but it keeps heat in the aquarium, and tends to get salt build up on it which allows the light to get blocked. It becomes something that needs to be cleaned frequently. Some people do not use a top which is good but the chances increase that you will have one of your prize fish go carpet surfing. There is another option and that is to make you own clear screen netting top. These tops are durable, will allow good air exchange, help keep your fish in the aquarium as well as minimal light loss. Making your own clear screen netting top is pretty easy. All you need to in order to make your own clear netting top is an aluminum window framing kit, and clear screen netting. The aluminum window framing kit can be purchased at most local hardware stores. 
Aluminum Window screen kit can be purchase at your local hardware store. The clear screen netting can be purchase from my store. http://www.aquariumoverload.com/itemsforsale 
You will also need a hack saw, a roller, a flat blade screw driver and a rubber mallet can be useful. The first thing you need to do is to measure the size of your opening of your aquarium to determine what size clear screen netting top you will need to make. Remember that the plastic corners take up some space you you need to subtract those from your measurements to get the length of the aluminum framing that you will need to cut. Once everything is measured cut the pieces to length with your hack saw. Once cut you can assemble the corners. A rubber mallet may make it easier to install. Test fit the frame on your aquarium and make sure if fits properly. Then cut the clear screen netting and make sure you leave a little overlap. 
Next you will install the cord. A roller is the preferred way to install but you can use a flat blade screw driver if necessary. Try not to pull it too tight as you might break the clear screen netting. Once all the chord is installed you can trim the excess mesh off. The top is now completed.
Finished clear screen netting aquarium top. Install your new top on your aquarium. This top was installed on a 37 gallon cube aquarium. 
That concludes this DIY. Thanks for reading