When you say your water levels are okay...can you be more specific? Have you tested the levels of ammonia, nitrate and nitrite? Temp? Ph? I've heard others characterize neons as being *VERY* sensitive, but i haven't had any problems w/mine in the year and a half that i've had them. I think if 3 out of five are dead in one week, you either bought sick fish or there is something wrong w/your tank.