Here is the thread with link to the Miami/Broward store list and google maps locator. It is an excellent tool, and will show you all the stores close to you.
I would recommend Exotic Aquariums on Bird Road: probably the biggest in stock selection of equipment in Miami Dade county, and it is pretty close to you if you just hop on the Dolphin east to the Palmetto, and South to bird road. Its only a couple of blocs east of the Palmetto off ramp. Of course, while you are on Bird road, you might as well hit the other 4 stores on that road. Hard to beleive, but there really are 5 fish stores with marine stuff on Bird.