Posted: Thu Sep 17, 2015 10:41 pm Re: Fluval fx6 res tank
One of the functions of a filter is to facilitate the bacteria for the nitrogen cycle, ammonia -> nitrite -> nitrate.
There are two different sets of bacteria that handle this, that can take weeks to completely establish an equilibrium in a new tank.
Of you have no ammonia, it means you have enough of the first type of bacteria. If you have nitrite, it means you don't have enough of the second. It's there and will grow, but it may take time.
Tobi a RES born in 2012
1 dog, 1 teenager, 3 aquariums filled with fish, snails, shrimp and a bit of algae