Second that - chemi pure is carbon, the elite has some gfo thrown in. It also is supposed to contain some 'de ionizing' resins, but from everything I've read that isn't going to help much in saltwater - they will be depleted almost immediately.
So, no need to use both. Chemi pure is simple to use and convenient, and if you have a small tank may be relatively cost effective. Otherwise I would suggest going with a high quality carbon that can be purchased more in bulk ..... I use rox 8 from BRS.