Since no one asked, when you test your water, what are the results?
Ammonia?
Nitrite?
If you show 0 for both, you have enough bio media now.
You can add more, but it will have no effect on getting your water clear.
Not sure how someone could recommend adding bio media without any basic information.
Would guess you need more mechanical cleaning as was already mentioned.
The suggestion of a Magnum HOT 250 is a good one.
The micron rated cartridge would probably clear your tank in 1-2 days, for a whole lot less money than a FX5 or diatom filter. Much easier to clean as well. With an extra cartridge, you could have the filter running continuously. One cartridge soaking in beach and water for 12-18 hours, then left to air for a few days. If the bleach makes you nervous, a soak in a dechlorinator could ease your fears.
Getting more turnover would not hurt, but without media that can trap all the really small particulate, all you would be doing is moving dirty water around.