Yup, IC ballasts are great and so is there customer service. No, you couldn't keep a fish that only eats xenia. As scooter said, it will probably wipe out the population. Another problem with xenia is that it will completely crash for no apparent reason and every stalk in the tank will melt. You better see if you can grow the stuff first anyways. I couldn't keep it alive for longer than a few months during my first couple years. Then, all of a sudden I got the stuff to take off like a weed. I had a dedicated refugium using only xenia for nutrient export and I was trading in 25-50 heads a month at the LFS. Xenia is some strange stuff. Some can't grow it and some can't keep it under control. I've experienced both.