How to cycle a new tank with bio-substrate

Bio-substrate carries the bacteria a new tank lacks. The job is to keep them alive from bag to floor.

1. Lay the dry floor

Pour the dry sand or gravel and shape the slope. Leave a hollow where the bio bag will go, or plan to spread it across the bottom.

2. Add the wet bag

Open the bio-substrate last and pour it in with its water — don't rinse it. Use one wet bag for every four dry bags of the same colour, or use it alone in a nano tank.

3. Fill gently

Put a plate or bag on the floor and pour onto it so the water doesn't scour the substrate. Start the filter and heater.

4. Add fish gradually

The bacteria start converting ammonia straight away. Add a few fish first, test the water, and stock up over the following weeks.