Recently all the fish in my aquarium died after a siphon accident forced most of the water out of the tank. Long another thread. Anyway, its been a week since the last fish died and I've been taking readings and using ammonia to get the cycle back on track. I've been putting in enough ammonia to take it to 2ppm. I've been doing this every morning and when I get home from work ammonia and nitrite are at 0. So I thought I was good but today I tested Nitrate and they are also at 0. Is this normal?