Does anyone use one of these and if so do they work? How good? Are they worth the money?

I use a nitrate filter.... caulerpa. Also sargassum and gracilaria. They work great.

This explanation is for freshwater, but if you exchange the word 'macroalgae' for 'vascular plant' it's basically the same thing: http://theaquariumwiki.com/Plants_and_B ... Filtration