My wife takes my dig. camera for vacation so I'll try to explain to you. It's not really a DIY project unless you overdrive the bulbs. Basically, you just buy a glass cover for 10gl tank (at Petsmart, maybe Walmart) or cut yourself a piece of glass to cover the top. Remove the original light fixture from the plastic cover and place it on top of the glass cover. Then, just buy another 20" light fixture (I use Coralife Slimline from Petsmart) and put it in front of the original one. So basically the top of the tank is covered by light fixture. You can get 20" light fixture at Home depot or fish stores. Since I want a very high lighting, I overdrived them following this article :
Just follow the second diagram if you decide to go for it.