Stocking Fish in your Tank

Cycling your tank

Once you have your fish tank set up you need to start the Nitrogen cycle going in the tank.  All new tanks need to establish a cycle to be able to provide a healthy living environment for the fish.  

What is the Nitrogen cycle?

Fish excrete Ammonia into the water and this is toxic.  Nitrifying bacteria need to build up in the tank to convert the Ammonia into Nitrite (which is also toxic to fish). As different sorts of bacteria begin to grow in the tank the Nitrite is then converted to more harmless Nitrates.  

Fishless Cycling

We recommend Fishless Cycling which is done with the aid of products that help you to start the Nitrogen cycle without adding fish:  

  • Filter Boost Water Treatments which encourage the growth of bacteria
  • Ammonia Removers which combat excess ammonia

You can check to see if your tank has cycled successfully with testing kits that measure the Ammonia, Nitrite and Nitrate levels in the water.

Visit our fish Products section for a range of water treatments and conditioners

Hardy fish 

Once your tank has stabilised you can start building your community of fish gradually, adding a few at a time.  This way the bacteria in the tank can adjust to the changes and the balance is not upset or overloaded.  There are a few hardy fish which we can recommend to start off with that will tolerate higher amounts of toxins in the tank such as Danios and Mollies.  Our staff will be able to give you accurate advice tailored to your needs in store.

View our Types of Fish section to learn more

Stocking your tank

You'll need to make sure that the types of fish you have chosen will get along with each other.  Certain types of fish can attack other fish and our staff will be very happy to give you advice about which fish are compatible with each other in store.  

Tropical fish

One good tip is to choose fish that swim at different levels of the tank, which makes the most of the space available and also gives a good display.

  • Top level fish: Common Hatchetfish, Siamese Fighting Fish (Betta)
  • Top to Mid level fish:  Gouramis, Swordtails, Guppies
  • Mid level fish:  Tetra, Tiger Barb, Glassfish
  • Bottom – Mid level fish:  Clown Loach, Discus
  • Bottom level fish:  Corys, Catfish

View our Types of Fish section to learn more

Cold Water fish

Some fancy goldfish are slow swimmers and should not be mixed with other goldfish varieties that are fast and agile as they will have a hard time competing for food:

  • Slow Swimmers:    Black Moor, Bubble Eye, Celestial, Chinese Lionhead, Pearlscale, Tosakin, Fantail, Oranda and Veiltails
  • Fast Swimmers:  Common Goldfish, Shubunkin and Comet 

Smaller fish such as the White Cloud Mountain Minnow and the Danios are best kept in schools of 6 or more.  Fully grown fast swimming Goldfish will eat smaller fish like the Minnows and Danios so we do not recommend keeping them together.

View our Types of Fish section to learn more

How to add fish to your tank

When you buy your fish, they will be netted and put into a plastic bag, with a little water from their tank.

  • Once home, turn your aquarium lights off as this will help to reduce stressing your new fish.  
  • Rest the bag on the water in your aquarium for 15 minutes.  This lets the water inside the bag adjust to your tank's temperature and avoids giving your fish a shock.
  • Add a small amount of tank water to the bag (this helps to balance the pH and prevent a pH shock to the fish).  Leave for a further 10 minutes.
  • Ideally net the fish out of the bag.  The fish will have defecated in the bag and the water will be full of ammonia, carbonic acid and thus a lower pH so it's not a good idea to add this water to your tank!
  • Leave the fish to settle in for a few hours to get used to their new surroundings.
  • Turn the aquarium lights back on and then give them a little food.