Cycling a Tank: The Fortnight Everyone Skips

A new aquarium is not ready for fish on the day it is filled, and this is the single most common reason new tanks fail.

What cycling is

Growing the bacteria colony that converts ammonia to nitrite and then to nitrate. Until that colony exists, waste accumulates as ammonia, which is toxic.

How long it takes

Typically two to six weeks unseeded. Adding mature media from an established filter shortens it considerably.

How you know

The tank is cycled when ammonia and nitrite both read zero and nitrate is present. That is a test kit answer, not a visual one.