Cloudiness in a new tank is likely bacterial bloom ... esp. if you did not cycle the tank before hand. It is more important to get the cycle established than clear the water. Please read up on cycling in the articles section (esp. if you already have fish) & maintain good water parameters during the process. Once the cycle is done, the water will clear on its own.
The Magnum is good for larger stuff (like algae bloom) but not really useful for bacteria. <I wouldn't bother with it during cycling.> I also just use the water polishing filter on its own (no diatom powder) & it does a good job. You need to clean out the filter once it gets clogged (maybe a couple hours if I have stirred up a lot of stuff) or it won't work at all.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.