Okay, you're in "gotta fix it now" mode, so might as well roll up your sleeves and get to it.
First, vigorous particulate filtration. If your filter system has a place to put a Polyfilter or some such as the first stage, go ahead and do it. Clean the sponge used for a bubble trap in the sump if you have one, get a filter sponge in the sump before return pump if you don't. Adjust your skimmer to a "slightly wet" skim to pull as much out on each pass as possible. Remember you're going to have to keep up with adding some additional saltwater during this period.
If you happen to have something like a Marineland Hang On Tank Magnum or an old Diatom filter or some such, this would clear the water pretty darn quick in your set up. nice to have one on the side for occasional water polishing if desired.
That's the first "step".
Second, if you can prep enough water for a healthy water change, say about 50%, do so. Let it mix for 24 hrs to stabilize and match temperature before the water change.
Do you use particulate filter media of any kind? Sponge for a bubble trap in your sump? Polyfilter or some such? If so, during the water change, change out/thoroughly clean the particulate filter. Again. Perhaps twice a day. If you have -any- other filter media, such as bio balls, ceramic stars or some such, this is a great time to rinse them out in a -saltwater- bucket as well.
While I see you're not, if you were dosing any carbon sources (vinegar, sugar, vodka, biopellets in a reactor, etc.): stop, pull the reactor(s)/dosers from the system, clean them and let them sit to the side until things get stable in the aquarium again. If you are dosing Kalk in your top off, I think it may be a good idea to continue as it has a tendency to bind phosphates.
Do the water change, use a clean particulate filter, and don't feed the aquarium for a day or two (believe me, they can handle it). Consider hooking up activated carbon and/or Polyfilter to pull organics out of solution. Observe the inhabitants.
Maintain vigorous particulate filtration over the next few days, and things should stabilize very quickly.