I run a few HOTs and use one for vacuuming and spot polishing. You can kick up the effectiveness of the micron cartridge if you add DE.
I usually put the blue sleeve around the micron, fill the filter and then add two heaping tablespoons of DE outside the sleeve.
When you turn on the filter, you will get an initial shot of DE out of it. Don't worry, it quicky disappears and causes no harm in the tank. Talk about sparkling water. (One note- because you are making the filter take out even finer particles, it will need cleaning more often than w/o DE.)