xenia does utilize nitrogenous compounds when growing, but for speed of growth actual LB per LB consumption your better using macroalgaes, but if you like xenia its like a nice little perk. keep in mind though it only really works if you harvest it. if uyou let it grow klike crazy all the waste consumed is still there locked in its flesh, if you expirience a die back (common with xenia) it all gets dumped back into the tank at once.