To OP, we were asking about your tank type because the biocube variety of 29g tanks with a plastic canopy are usually better off with a DIY retrofit kit like BladeYamaha posted. The complete LED fixtures are mostly intended to be mounted several inches above the water, more than a 29g biocube canopy would allow.
That said, nearly all of the most reputable LED lights are being made with 5-watt and 3-watt LED's manufactured by CREE with some of the colored (i.e red, green, etc.) coming from Osram. Some of the better lights are the Ecotech Radion's, the AI Sol's, Maxspect and GHL just came out with one, if you look at what type of LED's they use you'll see they're all 5-watt or 3-watt CREE's with maybe a few Osram or Phillips color accent LED's. So with that knowledge find one that best matches your particular desires. They're all good and mostly using the same components, some have more features than others like having a built in controller.
I do recommend you stick with a well-known brand with a good warranty and buy from a reputable retailer with good customer service. The ultra cheap LED lights you may see on eBay or Amazon all cut corners that reduce the efficiency and lifespan of the light. When you find one you're interested in post a link and we'll give you some more feedback.
