Cold water tanks are actually unheated tanks that are not necessarily cold, just room temperature – a fact that’s perhaps unfamiliar to those who are just beginning to keep fish.


Unlike tropical aquariums, you don’t need to provide a heater for your cold water fish tank, however, it’s a good idea to use a thermometer, so you can ensure it’s kept at a nice comfortable, constant temperature for your fish.

You’ll need to buy a filter for your tank, as well as a lid, light, and a pH testing kit. Your cold water fish tank should also include a few plants and decorations, so there’s plenty of space for your fish to explore or hide away if they wish. Make sure the plants are suitable for the types of fish you have, or if you have plastic plants, make sure they’re appropriate for fish tank use.

You’ll need to ensure your cold water fish tank is cleaned every week. This is much simpler to do than you might think – you shouldn’t remove any fish or objects from the tank, as this can disrupt the natural bacteria and even cause unnecessary stress to your fish. For more details on how to clean your tank, take a look at our guide.


Much the same as fish flakes, fish food pellets are a good stable food source. You can buy different types to suit where your fish like to find their food, whether that’s on the surface of the tank, in the gravel, or mid-way between.


The lifespan of cold water fish will vary depending on their species, but in general, they tend to live for around five years.


Most cold water fish are sold when they’re very young, so you should bear in mind that they’ll most likely grow a considerable amount. It’s important to make sure you’re aware of just how big they’ll get, so as to avoid an over-crowded tank.

There are many different cold water fish types to choose from, but species that are great for those just starting out include: Bloodfin Tetras and White Cloud Mountain Minnows.

Please note all Care Advice is provided courtesy of The Pet Charity  and OATA. Further information can be found on their websites.

Goldfish are typically trouble-free pets for all the family to enjoy. A well cared for goldfish can live for eight years or longer, so do be prepared to upgrade your tank as they grow larger.

There are many varieties to choose from ranging from the common goldfish to varieties such as Comets, Fantails, Orandas, Lionheads, Shubunkins and Moors. These fish can all be kept in a tank or pond at room/outdoor temperature, so it is unnecessary to heat the water.

General care

Healthy fish are bright-eyed and have a shiny appearance. First signs of distress are usually sluggish movement and drooping of the dorsal and/or tail fins.

The most common illnesses are fungal infections of the skin, parasites and constipation.

Loss of scales, split fins and wounds received from predators can cause infection. Injuries can usually be treated with one of the many preparations available for this purpose. Your pet shop or aquatic centre will be able to advise you on the many proprietary remedies available.

Choosing your goldfish

Goldfish varieties can be mixed but all fish should be of a similar size and be compatible for water temperature and feeding habits. You should not mix single tailed and twin tailed goldfish, and it is important to remember that twin tailed goldfish are only suitable for an outdoor pond in the summer months. It is recommended that you find out how big your chosen fish are likely to grow.

A healthy goldfish should:
• Swim easily through the water and be active
• Not gasp at the surface of the tank or swim in a peculiar manner
• Have scales that cover the body evenly without any cuts or growths


There is a large variety of aquaria, ponds, equipment and accessories available to make fish-keeping even more enjoyable. All manufacturers give good advice on the installation and maintenance of equipment – it is important to follow their instructions carefully.

Set up your indoor aquarium at least 24 hours to three days before introducing any fish.

Indoor aquariums

There is a great variety of designs and sizes to choose from, depending on the space you have available.

The tank must be placed either on a specially designed stand or a strong rigid surface, with an expanded polystyrene mat underneath the tank. Ensure the surface will be able to hold the tank once it is filled with water. Position the tank away from windows, as daylight encourages algae growth, and also away from heat sources. A full tank can be very heavy, so never move a tank containing water. Handle with great care and transport horizontally.

Setting up your tank

• Thoroughly rinse your new tank with clean water, then cover the bottom with carefully washed gravel and slowly fill the tank with water.
• You may also wish to add some aquatic ornaments, rocks and plants. Live plants will need to be trimmed regularly.
• Always use a water conditioner to make the tap water safe.
• A filtration system is always recommended.
• Introduce the fish only when the water quality is suitable.
• Your retailer will advise you on the number of goldfish you should keep in your chosen set-up.


You must remember to test the water quality in your tank regularly, this is because cold water fish are unable to tolerate high levels of ammonia or nitrites, which your filter will breakdown to a safe level. You can purchase water testing kits at most pet shops or aquatic centres. The more attention you pay to your tank’s water quality, the healthier your fish will be. It is also important to remember that it is not true that if the water is clear the quality is fine – this is a myth.

Aim for your tank water to reflect the following:
Temperature: 18-24°C – most goldfish are happy at room temperature so long as it doesn’t fluctuate too much.
pH level: 6.0-8.0
Ammonia and nitrite levels: 0mg/l

Water changes

Tap water should always be treated with a water conditioner, which your pet shop or aquatic centre will be able to advise on. For systems with a filter, carry out regular 25 per cent water changes, with a complete water change when necessary. Filters should be cleaned by rinsing them in the waste tank water, not under a tap. For systems without a filter, change half the water weekly and a complete water change every month.

Introducing your fish into the tank

• Turn the tank light off, keep noise and movement to a minimum to help reduce stress.
• Float the unopened bag in the top of the tank for at least 15 minutes to regulate any temperature differences – this avoids shocking the fish.
• Open the bag and slowly allow some tank water to enter it so your new fish can get used to the difference in water. Wait a few minutes, then allow more tank water into the bag before gently releasing your fish into the tank.
• Turn the light back on after two hours.
• Seek advice from the retailer when purchasing your fish and ensure you are introducing compatible species.
• Do not add too many fish at once, as this puts too much pressure on the filter and fish can suffer. Check your tank’s water condition is optimum before adding any further fish.


Feed daily according to the manufacturer’s’ instructions and be careful not to overfeed. Provide suitable food for all species of fish in the tank. A good rule is to feed your fish the amount they are likely to eat within two minutes, to prevent uneaten food rotting at the bottom of the tank.


Handling fish should be kept to a minimum and cause as little stress as possible. Use a net to catch the fish – gently corner it and catch it quickly. Place the fish gently in a holding receptacle that contains water from the tank.