Nice, I've heard that they are very good at nutrient exportation, and was planning on partitioning off a section of my refugium just for them to grow. Actually an article in Marine Fish & Reef has a Caulerpa vs. Xenia chart kind of like this:
Caulerpa Xenia
Nitrate+Nitrite 107.0 .6
Ammonia Nitrogen 113.7 585.0
Total Nitrogen 1016.7 8600.0
That is the amounts of nitrogenous wastes removed per kilogram of export material. I figure having a good stock of both should be really beneficial to the tank. My refugium is 30gal, I'll probably partition a quarter of that just for the Xenia. Put some rubble on the bottom and just let it go crazy.