You need to get some fish TODAY! If you don't puting some seeded gravel in the filter isn't going to do any good. The bacteria that's in the gravel needs something to feed off of, I.E. fish waste. Other wise it's just going to die and you'll be back to where you were before you got the gravel. Your plants need the fish waste as well to use as a food source. Go get a few fish today. Get some hardy fish like swordtails, Zebra Danios.
Rose
Rose