500 gallons. Wow!

Sounds impressive!
I'm not sure, but it sounds to me like you have a bacterial bloom. I also use Vortex diatom filters, and in my experience, they won't help with a bacterial bloom at all. It should clear up on it's own fairly soon. However, it definitely won't hurt to try and use the diatom filter. Vortex claims that they can be used continuously, so I'd just charge it up and put it on the tank and see what happens. I have used mine for a couple of days before when I wanted to clean the water thoroughly after medicating the tank (also had the Vortex Super-Char activated carbon in it for absorbing the chemicals). I think that if you go ahead and add the plants that the water will clear up a little quicker, but again, I'm not sure.
Good luck! I hope you start a journal so I can enjoy your tank too!
Andy