My 40g breeder tank with 1 small arowana has been set up for about a week now and the nitrite is reading 0 and the ammonia is reading .5. I have a penguin 350, a pump, and a heater at 82 degrees. I've been following the directions on the stability bottle. Are my readngs normal? When should it clear up? Should i do a water change? %? Is an ammonia reading of .5 THAT harmful? Thanks.