To get a jungle look slope your gravel from the highest (about 2") at the back to about 1" at the front. Put tall plants at the back graduating to small ones in the front. If possible use real plants - IMO looks much more natural. Find a nice piece of bogwood for the centre piece, a few more stones for the fishies to hide in, and wait for the plants to grow. There's no need to take the fish out when you rearrange your tank - just be careful not to squash anyone.