How to Set Up a Freshwater Aquarium

What you need first

Choose your tank size and your animals before you buy equipment, because they decide your filter and heater. You will also need gravel or another floor, decor, a water conditioner, a thermometer and a test kit.

Many species pages list gear for their tank size. Try the fish list to start.

The order that matters

1. Pick the spot

   A veterinary manual says the floor and stand must be strong, level and stable, because water is very heavy. Keep the tank out of direct sunlight, and a trade association adds heat sources, draughts and loud noise. Check you can reach enough outlets, and our filter and heater guide covers electrical safety.

2. Wash the tank

   A veterinary hospital group says to wash it out to remove dust and debris. Use plain water.

3. Rinse the gravel

   A veterinary manual suggests about 1 pound per gallon, and says to rinse it thoroughly first, since dust can clog filters and damage pumps.

4. Add large decor

   Rocks and driftwood are easier to place before the tank is filled. Decor can also divide the tank, so that fish can hold their own territory.

5. Fill and treat the water

   Tap water usually contains chlorine or chloramine, which a veterinary manual says are toxic to fish and to the tank’s helpful bacteria. Use a dechlorinator that treats both.

6. Switch on the equipment

   Only once the tank is full. A veterinary manual says filters, pumps, heaters and lights should not be turned on before then, and warns that heaters may shatter out of water.

7. Let it settle

   A trade association suggests leaving a new setup for 24 to 48 hours, so the temperature settles and you can see that everything works. Check with a separate thermometer.

8. Cycle the tank

   This is the step beginners skip, and it matters most. Our cycling guide walks through it.

9. Add animals slowly

   A trade association warns that stocking too quickly can cause new tank syndrome. Use our stocking checker to test your plan, and see how to acclimate new fish.

Lights

Fish need a day and night cycle. A veterinary manual warns that leaving lights on around the clock stresses fish and leaves them open to disease. Too much light also feeds algae, which our green water guide covers.

After setup

Set a routine as soon as the tank is running. See how often to change the water. A trade association also warns that each time you add fish or feed more, the filter’s bacteria need time to catch up, so keep testing.