Just something to think about...Sponges and bio-media are not going to be very good for your system if you plan on keeping anything besides fish. These things tend to be too good at producing nitrates from waste, thus causing high nitrates. The better choice for bio-filtration is live rock - about 1-2 pounds per gallon.
Getting back to the cloudiness...
It sounds as if the filter materials you are currently using is not fine enough to remove the small, dust-like particles. If after another day or two, you don't see any significant improvement, you'll need to find something that will filter them out. Your LFS should have filter felt. Maybe you could install some in the filter you already have. I run 100 micron in mine 24/7.
Even if the cloudiness settles down on it's own, you will probably stir it up again every time you disturb something in the tank.Better to try and filter it out now, IMO. A canister filter may also be something to try. I've never owned one, but I believe it would help your situation.
Also, on a side note, you'll want to increase your salinity to about 1.025-1.026.