If I understand you correctly, you now have a (default) judgment against the defendant for $20,000 (probably plus costs and a year's worth of interest).
Unfortunately, you have come to the hardest part of litigation: collecting on a judgment. We worry so much about winning the case, and ultimately get a judgment, but the judgment is just a piece of paper.
The first thing you need to do is locate the defendant. Is he still in your area? If not, can you have him traced to where ever he is now? Some people are experts at this: a good collection paralegal often is and many private investigators are.
If the defendant is still in Florida, you can execute on the judgment under Florida law. I am not licensed to practice in Florida, so you should get those answers from a Florida lawyer. It is my understanding that many collection techniques used in other states can not be used in Florida, so proceed with caution and with a Florida lawyer's advice.
If the defendant has moved to another state, you may need to "localize" the judgment against him. For example, if you find that the defendant has moved to Kentucky, you get a special form of the Florida judgment and file it in a Kentucky court. After you follow the required procedures, the Kentucky court will give "full faith and credit" to the Florida judgment and give you a judgment in Kentucky.
You can use that judgment in Kentucky as a basis for collection of the obligation under Kentucky law. If the defendant is working, you can have his wages garnished. If he has money in the bank, you can have that seized by filing a "non-wage garnishment." If he owns real estate in Kentucky, you can put a judgment lien on it. You can take any action to collect on the judgment that you could if the judgment was initially obtained in Kentucky.
Collecting on a judgment can be exasperating ... until you locate and seize an asset that pays the judgment, and all accrued interest, costs, [and attorney's fees if applicable].
The same will be true of other states. "Localize" the judgment, then execute under local law. [Judgments issued by federal courts are handled a bit differently; I have assumed that the Florida judgment was issued by a Florida state court.]
I agree entirely with Mr. Davis. I would add that there are collection agencies that will assume responsibility for collecting on the debt in return for a percentage of the amount collected. You may wish to explore that possibility, particularly if the defendant is no longer in the state.