I found a link to this thread on RC while doing some homework avoidance and thought it should be shared:

http://www.reefcentral.com/forums/showthread.php?t=1705322&highlight=chemi+pure

Here's the core to what he wrote when asked about using chemi pure:

"The so called synthetic media is a ion exchange resin like in a RO/DI unit. So, it is useless in seawater. ..................
Do you know how you regenerate a DI resin that removes ammonium ? You use table salt and seawater is 85 % table salt. So, how is that going to work by magic ?" - Boomer