Keeping Clown Fish

What are Clown fish?

Clown fish are colourful, cute and sometimes amusing inhabitants of tropical reefs from several places around the world, including the Great Barrier Reef. They are a hardy fish, and with the proper aquarium and care, can be safely kept in the home for many years.

Clown fish like “Nemo” are usually 2-8cm long. They have an unusual symbiotic relationship with sea anemone in the wild. While other fish may be stung and killed by the anemone’s tentacles, Clown fish are immune, living amongst the tentacles. They feed on the anemone’s leftovers, and can even bring it food. They are social fish, and as such it is recommended that at least two are kept in aquariums.

In the past, Clown fish for aquariums have always been caught in the wild from the reef. Today there are several Clown fish farms around Australia. It is strongly recommended that anyone wishing to keep Clown fish in a home aquarium insist upon aquacultured, or captive bred Clown fish. Captive bred fish do not create an impact on the natural environment, they are healthier and hardier, there is little chance you will buy them diseased or sick, and they are not fussy eaters.

Introduction to keeping

In the wild, Clown fish have a small territory, and therefore can survive in smaller home aquariums, but for a number of various reasons, bigger aquariums are better. As a minimum, a Clown aquarium should be approximately 40 litres. Setting up a marine aquarium is far more complex than freshwater, and mistakes can be deadly to everything in the tank. It is therefore very important that a marine aquarist is well informed, and committed to spending the time, effort and money to do it right.
Below is a list of equipment that you will need as a minimum to keep Clown fish:

  • tank – at least 30 litres
  • water – specialised artificial sea salt mix with a water ager
  • sand – small grained sea sand
  • 1kg of live rock per 20 litres of water at least
  • filter – almost any kind of mechanical filter will do (optional)
  • circulation – a small (100 litre per hour) internal pump to keep the water moving
  • ammonia test kit – to test the level of ammonia in the water
  • heating – 100 watts of heating per 50 litres of water
  • lighting – one or more fluorescent lights
  • thermometer – to test the temperature
  • hydrometer – to test the water salinity
  • nitrite test kit – to test the level of nitrites in the water
  • pH test – to test the pH of the water

Setting up the aquarium

  • Clean the tank of dust and dirt, and position it where it will be kept. Ensure that the tank will not be in direct sunlight for very long at any time.
  • It is very important to note that you never, ever use any cleaning products in, on or around your tank, as these chemicals can and will kill your fish. Always wash your hands thoroughly in water only before putting your hand in the tank, and do not use and aerosols, flea bombs or similar products in the same room as the tank.
  • Add sand to a depth of approximately 3-6cm average depth.
  • Pour seawater or artificial sea salt mixed with aged tap water to the tank, leaving about 5cm from the top (this is for the displacement of everything that is to be put into the tank).
  • Put in the heater, and only when it is submerged, turn it one and set it to 26 degrees Celsius.
  • Add the filter and turn it on.
  • Add the internal circulation pump and turn it on.
  • Let the cloudiness settle for a couple of hours and ensure that the tank temperature and salinity levels are correct. Clown fish require the salinity to be 1.026.
  • Add some live rock.
  • You may keep the light on for approximately eight hours per day but this is not essential until you add your fish.
  • Test the nitrite levels daily. For the first several days, the nitrites should be zero. You will eventually see a very high reading. After this, the nitrite level will slowly drop over several days or weeks. This process is known as the nitrogen cycle or cycling.
  • Cycling will take one to four weeks and you will not be able to put any living things into the tank until the nitrite reading is zero. This is because the levels of poisonous chemicals in the tank could be fatal to them.
  • When the nitrites have returned to zero it is safe to add the fish.

Maintaining your tank

Marine aquariums require ongoing maintenance. This is to ensure that the conditions in the tank are kept constant, and that the water quality is kept at its best level possible. The regular tank maintenance routine will include the following:

  • check the temperature
  • check that the circulation and filtration pumps are functioning
  • feed the tank a small amount of food


  • drain 10-20% of the tank water and replace with new sea water or mixed and aged tap water which has been heated to the same temperature as the tank (you may need a second heater to do this).
  • clean the physical filter by rinsing it in the removed tank water
  • top up the tank with aged tap water to make up for any evaporation
  • test the pH levels and test for ammonia.
  • for a week after any new tank addition, test nitrite levels. If they are high, you will need to do daily 10-20% water changes until they drop.

The Nitrogen Cycle

The most important component of a successful marine tank is a healthy bacteria colony. These bacteria thrive on exactly the chemicals which cause problems in your tank and the end byproducts are naturally removed, leaving your water safe for fish and other inhabitants. This is known as biological filtration. The bacteria reside on the live rock that you add to the tank and will quickly spread to the sand, along with worms and other helpful creatures.

In order for the biological filter to become established, it must first go through the nitrogen cycle. When you add the live rock to the tank, some of the living things will die and decompose, resulting in a high level of ammonia in the water. Ammonia is poisonous to most creatures. It is important to have a big “spike” in ammonia to start the cycle, thus the addition of the extra food.

In response to the plentiful new ammonia supply, ammonia-eating bacterial thrive. As these bacteria consume the ammonia over a couple of days, they create nitrites as waste. Nitrites are ales poisonous to most creatures and need to be dealt with. Fortunately other bacteria can help us out.

While your tank is ‘cycling’, you will notice a lot of growth of algae. This is normal, and you will probably see ‘wavers’ of different types of algae come and go in the first several months of the tank’s life. Algae blooms can be a problem from time to time but they are rarely dangerous and good advice from experienced tank keepers will help you deal with the problem.