i would put a filter. you're spending all the money on fish why skimp out. more filtration will never kill the fish it will only help them live longer
as i said before i have two filters, a marineland emperor 280 with biowheel and nitrogeon in a media cartrage and an aqueon 30 with bio stones in it. i also have a protien skimmer, my water perameters are always low and my fish are always happy.