In my 30+ years in this business, I have never heard of such a thing. The only thing this would do is allow you to go longer between filter cleanings. The "stuff" in your water that's making it so "crappy", is far too small to be filtered out with this type of filter. Me thinks you just need to learn how to more properly care for your spa.
Why not start with explaining what exactly your problems are, and telling EXACTLY what you're doing to maintain the water (including all the chemicals, the amounts you're putting in, and test readings).