nitrate levels

I started 2 tanks at once about 2 weeks apart. New tank is 32 biocube. I have a large Anubis and driftwood and running CO2. All natural gravel substrate recycled from 5 years ago. 3 fish living in it as I used 75% of the old water when I changed out tanks. Having a really hard time keeping it...

When I first rescued my Jack Dempsey, almost a year ago, he was very ill and I had to keep him in a ten gallon tank. (I was a new fish owner and never could get my levels to 0 or close to 0) Then after a few months, I bought a 55 gallon tank and cycled it for a month and a half. Then I...