Yeah, I had a little 18w tube on my son Oliver's tank and I wanted to do "low light method" and not the real high-tech stuff while we are still beginners. I couldn't absorb all the info about lighting fast enough and didn't want to make a wrong purchase yet, but I discovered that another identical light would fit perfectly, so how we have -two- little 18w tubes on our 28G which nicely puts us up over 1w/G hopefully sort of close to where we want to be. This was a great stop-gap measure for us.
There are clearly some great little companies out there on the web making various hoods (not sure what machine my bookmarks are on or if I even have them, sorry) - I think one I was looking at were Coralife (?) which I believe had some straitforward tubes in reflectors.
~~waterdrop~~