I know what you are talking about and those bulbs are only a few watts (15 or so I believe) and have a very wide base which I assume contains a mini ballast. I use two of them on my 10-gal QT tank when I have corals and such in there and they have worked fine for me. I've even managed to grow macro algae and coralline under these bulbs...something not easily attained with NO bulbs.
So, if your fuge is small and not very deep, then you could use these bulbs as a cheap alternative. You would still be better off with a few more watts in lighting in the future though.