If your tank is heavily planted already, you can start to add a few fish immediately. If your tank is planted sparsely, you can still add some small inexpensive fish to help with cycling your filter. That's a big tank, so a few small fish would be fine. Just don't go adding expensive, big, or many fish. By heavily planted, I mean most of the substrate is covered with plants, or most of the surface is covered with floating plants. You should get some pictures up so we can see.
P.S. This is assuming you have no ammonias already spiking in your tank because you added some chemicals to help cycle the tank.