What kind of hood do you have? Does it have a tube type bulb in it like a fluorescent bulb or a screw in type like a regular light bulb? Is your filter in your hood with your light or is it a filter that hangs on your tank?
If the filter is seperate from your hood I would look into one of these types as they are not expensive and they let enough light in for you to see the fish but not so much that Shadow will be upset with it. They also last a pretty long time and you can get replacement bulbs for them but it is generally cheaper to just get a whole new light.
You will need to get a cover for the tank if you do not use a hood though but what I would use instead of a glass cover is to get a piece of plastic canvas at a craft store and use instead. Measure the top of your tank and get a piece of plastic canvas like you make things with at a store like Walmart if your tank is really big you may need to get two pieces and tie them together with a couple twist ties in a couple places on each end to hold them together. It lets air in to the tank and keeps heat from building up and allows the fish to have light but also gives him a bit of a shadow effect from the canvas and cuts down on the amount of light.
Aquarium Lights & Decorative Lunar Lights: Hydor Multi Light LED Aquarium Light
Perch-Light Compact Fluorescent Aquarium Lighting Fixtures | Compact Fluorescent Straight Pin Bulbs | Bulbs & Lamps | Aquarium - ThatPetPlace.com
Any of these lights I would recommend that you get the help of a parent to set up as any time you work with an electrical device around water it is nice if you have their help to set it up.
Hope this helps.
Rose