I just started stocking my first tank, 29 gallons, fully cycled. I bought nine harlequin rasbora and 6 diamond tetras. My problem is that one of my tetras (the biggest and most beautiful one, of course) is harassing all five others. He pretty much leaves the rasboras alone, but he patrols the entire bottom of the tank and chases away any of the five that venture down below the top third. I now have 14 fish sitting at the top of the tank and one mean (but pretty) fish at the bottom. What can I do? Will buying another tetra or two help, or just exacerbate the problem? What about seeing if I can return this one problem fish and exchange it for another (hopefully less of a bully)? Thank you.