A 48" finnex ray II will give you some nice med-high output. Or you can roll with a 2x54W Catalina T5HO fixture. This all depends on which specific plants you want. Just note that its always easier and cheaper to reduce high lighting instead of adding more light. That's why I suggest a moderate-high fixture so you can just alter it to your needs and always have the option to up the lighting down the road incase you want to try higher light plants. If you are 100% positive you only want low light plants, a couple of stock aqueon t5 strips will suffice with the right bulbs (or a cheap fixture from a home improvement store).