I've got some caulerpa taxifolia you can have.
Extremely hardy, extreme nutrient export, easy to prune, but grows like weed. I find you can prevent it from going sexual in a main display by pruning it every other week or so (which again it needs anyway). It's in by biocube 29 and looks really nice, but can start to take over so you really need to stay on top of pruning.
You want to make sure you really want it, because I don't think there's any getting rid of it.