Halimeda: Are calcium based macros. You'll need to be dosing with calicum, but if you have a reef tank, you will be doing that anyway. It will removes nutrients from the water as well as function as a haven for pods, baby bristle worms, serpant stars, etc. It is not weedy. When the plant dies off, it leaves behind a white calcareous skeleton which, in nature, is a viable supply for reef sand. Can't think of any reason not to have this in a refugium. It is a great plant, as well as quite attractive.