A good chemical to use is neem oil. It's safe and natural- I use it on even my most sensitive plants. I had a mite infestation developing on a pygmy sundew of mine, but they all died within one treatment. I use Greenlite brand neem concentrate. Just dilute 2 tbsp per gallon of water and cover the whole plant thoroughly (including under the leaves, between branches, etc.). Depending on how hearty these little bugs are, you should see results within one to three treatments. Just don't get the oil on your carpet, as it leaves a rather... unique smell (something between lemon pledge and a dead animal) that is offensive to some people.
Another option is anything containing pyrethrins or systemic pyrethroids (sp?). Pyrethrin is extracted from chrysanthemums, and will quickly penetrate and damage an insect's nervous system. With mites, this dosage should be lethal, but it's best to keep applying just in case. Pyrethroids are like pyrethrins in their attack plan, but they are systemic.
Finally, you can use orange oil treatments. Orange oil is the hardest to find, in my opinion, but the best. It just smells like oranges, and works quickly to break down the insects' respiratory systems, causing instant death to whatever comes in contact with it. The only downside is that it is, being orange oil, extremely biodegradeable, so it will need to be reapplied quite a bit, to kill future generations of mites.
I hope that this helps, and good luck with your ficus!
There's just something alluring about a tiny, hungry mouth determined to catch and digest alive six-legged prey. Call it a quirk.