My giant turbo snail died. I guess a day or so ago. Anyway I found him during a normal water change today. I did notice that it was pretty smelly where the tank is. Anyway I did the WC and removed the snail. (This guy was BIG) before the WC I took a sample and tested for ammonia. It was .25. With the 10 gallon WC and carbon in a reactor, how long before I should see it back to zero?