chaeto... is over rated. get any type of macro algae and you will be fine. my recomendation is to get Caulerpa. that is the type that looks like sea grass it has long blades of grass if you will. there is two types of Caulerpa the regular one and the feathered Caulerpa, both which tangs love to eat and you will kill two birds with one stone, help remove nitrates and feed tangs greens. also i dont know how well you know the whole fuge thing works, but you have to periododicly "clip" and remove and throw away the macro to remove the nitrates. well enought talking... GL