The six weeks before the first fish decide whether a tank works. Here is what is happening in the water, and what to do each week.
A new tank looks ready the moment it is full. It is not. Fish produce ammonia, and a new tank has none of the bacteria that turn ammonia into something harmless.
What the cycle is
Two groups of bacteria do the work. The first turns ammonia into nitrite, which is still toxic. The second turns nitrite into nitrate, which plants use and water changes remove. Growing both colonies takes four to six weeks.
Week by week
Week one: fill the tank, run the filter and heater, and add a bottle of live bacteria and a pinch of fish food every day.
Weeks two and three: test every other day. Ammonia will rise, then fall as nitrite climbs.
Weeks four to six: nitrite falls to zero and nitrate appears. When ammonia and nitrite both read zero for a week, change half the water.
The first fish
Add a small group, feed lightly and test for another fortnight before adding more. Patience here is the cheapest equipment you will ever buy.
