Fish are very relaxing and beautiful to look at and many species are kept for these reasons. They are suitable pets for people living in flats or other confined areas, but for people with plenty of outdoor space an in-ground fishpond can enhance a garden setting.

Whether kept in an aquarium or pond, a great deal of care is required in looking after fish properly in terms of facilities, time, financial means and level of interest.

Particular attention must be given to water surface area, temperature control and water quality.

Choosing the type of fish you intend to keep

The type of fish you keep will depend on the amount of space you have, and the amount of money you wish to spend on their purchase and the equipment associated with their care.

There are two broad categories of aquarium fish; freshwater and saltwater (marine) – and within each of these categories are coldwater and tropical varieties. Coldwater fish are suitable for coldwater aquariums but tropical fish need heated water.

Outdoor pond fish are normally of the freshwater-coldwater type.

It is important that all indoor fish be kept in a properly set up aquarium and not small bowls. The main reason for this is that the fish bowls have a small water surface area and therefore limit the amount of oxygen entering the water. In a bowl it is much harder to keep the water clean and maintain good water quality.

When selecting fish, buy only healthy specimens and be sure to purchase your fish from a reputable dealer (dead fish in the sale tanks indicates poor health). Beginners should start with a freshwater aquarium and a few coldwater fish. Choose hardy specimens such as goldfish (a good variety being a comet and avoid the fancy breeds).

Tropical freshwater fish suitable for beginners include platties, swordtails, guppies and mollies. Be sure that you know how to keep fish properly before buying tropical fish because they are more sensitive to poor water quality and temperature fluctuations.

Saltwater (marine) tanks are more difficult to manage than freshwater tanks. This applies to both cold water and tropical marine tanks. These should not be attempted by beginners.

Tropical marine fish suitable for aquariums include clownfish, wrasses and tropical seahorses. Seahorses can be difficult to feed properly as they often require specialised food.

Before purchasing fish, ensure that the species of fish you intend to keep together have the same water temperature and water quality requirement. Incompatible fish will not be able to be housed together – tropical and cold water fish cannot be kept in the same tank, for example, as they have different water temperature requirements. Large size differences between fish may result in some fish inadvertently eating others in your tank. Some fish species are also more aggressive than others, and this may make them more difficult to keep in groups.

For advice talk to a reputable dealer and also contact your local Aquarium Society. Members are usually very helpful with advice, equipment purchases and sourcing of suitable fish.

Care for your fish

Setting up an aquarium

A fish tank should be an appropriate size for the number of fish held and the species being kept.

A tank should be large enough to adequately accommodate the biological mass of the fish and plants within. Fish bowls cannot do this adequately. Instead, a tank large enough to accommodate a filter system should be used. A general rule is 4 litres of water per 1 inch of fish. A common concern is that a large tank will cause small fish to be stressed – this is not the case, the tank cannot be too large for fish, larger is always better.

The number of fish a tank can accommodate is also related to the filter system that is in place, as well as how regularly it is cleaned and how well it is maintained. A regularly cleaned tank can house more, healthier fish, than one that is not looked after.

The volume of your aquarium in litres can be calculated by using the following simple formula. All measurements are in centimetres.

Volume = (length x depth x width)/1000.

When adding water to a freshwater aquarium, dechlorinated tap water should be used. Water straight from the tap contains chlorine, which when untreated, is potentially harmful to fish. A commercially available water conditioner/dechlorinator, such as Seachem’s “Prime”, should be used to make the water safe for the fish. Additional good bacteria can also be added, Seachem’s “Stability” can be used for this. Seawater is best made up from bottled water or tap water with the addition of special sea-water mix available from aquarium shops. Water from the ocean should not be used, as it can carry potentially harmful diseases to your fish.

Step by step Instructions

Starting with an empty aquarium, place the glass tank on a piece of foam, long enough and wide enough to cover the entire bottom of the glass tank. This can then be placed in a tank stand, or on a solid, flat surface. The foam provides some padding and allows for a small amount of flex in the glass, when heavy objects such as rocks are placed inside the tank.

The tank should be positioned in a well-list area, but not in direct sunlight. Direct sunlight will heat the tank water too much during the day and it will cool too much at night. This increases stress to the fish, putting them at risk of disease, and encourages algae growth, making the tank difficult to keep clean. Remember that one litre of water weighs one kilogram and there is the additional weight of the tank, stand and other equipment. The floor surface and stand you have chosen must be able to support this total weight. If you live in an apartment that is above ground level, you may need to check with your landlord or body-corporate that the floor will be able to accommodate the tank.

First, half fill the aquarium with water (clean tap water is suitable). Use a new clean plastic bucket that has been rinsed and washed with tap water before you use it. Keep this bucket solely for your aquarium use. Do not use the laundry bucket as this may have traces of chemicals that may harm the fish.
The best substrate generally is river sand. The small grains have a good surface area for good bacteria to grow, it is easy to clean with a siphon, and is a good substrate for most fish species. Stones and plants can then be added. Plants will need to be weighted down with gravel or stones. Consider the fish species you are setting up for – some species, such as neons, like to school in open spaces, while other species, such as ghost-knife fish, require a tube to hide in.  Plants will help to oxygenate the water.
Complete the filling of the tank to within five centimetres of the top. Fish may jump out of the tank, so cover the aquarium with a glass or wire top that is raised sufficiently to allow air circulation.

Read the instructions on your aquarium decholrinator, and add the amount required according to these instructions. It is important to do this before adding any fish to the tank.

All fish tanks require filtration. A filter takes in tank water, removes large and small particles floating in the water – food, fish waste and plant material, and then pumps clean water back out into the tank. This process can only happen effectively if there isn’t too much waste in the water for the filter to cope with, and the filter is cleaned regularly to remove the waste that builds up inside it.

Internal filters are available – these are generally only suitable for very small tanks, with a small number of fish. External filters are preferable – this is a large, external canister, connected by an inlet and outlet tube, to the fish tank. Internal filters must be cleaned weekly, where external filters can be cleaned every 1-2 months, depending on the amount of waste that builds up.

Adequate filtration will reduce the amount of waste products in the tank, keeping the water clean, maintaining good water quality, and keeping the fish healthy. When cleaning a filter, wash the internal filter media in a bucket of water taken from the tank. While it is tempting to rinse it under the tap and make it look very clean, this will also wash away any good bacteria that is helping the filter to clean the water. Washing the filter medium in water taken from the tank helps to preserve this.

Placing the filter outlet near the top of the water helps to create movement across the surface, which assists in aerating the water. The filter inlet should always been down near the bottom of the tank, so that the filter will move the water to circulate around the tank, preventing waste accumulating anywhere in the tank.

Further aeration can be added if required. A small air pump can be used, and an air stone placed on the bottom of the tank, to move air through the water.

For tropical fish, a heater and thermometer are also needed to keep the water at the right temperature (22° C – 24° C for tropical, freshwater and marine fish and 15° C – 20° C for coldwater fish). The effects of central heating and other forms of room heaters should be considered. Water temperature in tanks should be checked daily and maintained within a range of 3° C of the optimum temperatures.

Let the newly filled aquarium stand for about 3-4 days before buying your fish. It is important to add dechlorinator or conditioning salts at the beginning of this time.

Fish are usually sold in a plastic bag and this should be floated on the surface of the tank water for about 30 minutes to allow the water and fish in the bag to reach the same temperature as the water in the tank. This way, fish will not get a shock by being moved to water at a different temperature. A sudden temperature change of even a few degrees can kill the fish. After this time, add tank water very slowly into the bag to allow the fish to acclimatise to the tank water (and thus prevent osmotic shock). Leave the fish for another 30 minutes in the bag and then carefully pour the fish into the tank.

New aquariums take at least six weeks to ‘settle down’ after the fish have been added. Fish excrete ammonia into the water, which is potentially toxic. This ammonia is converted to nitrite (which is also toxic to fish). The nitrite is then converted to more harmless nitrates. This is known as the “nitrogen cycle”. The effectiveness of the this cycle is what is referred to as “water quality”. Good water quality is when the  pH level, ammonia, nitrate and nitrite levels are all within safe parameters for the fish species you are keeping. This can be measured using a water testing kit, available from pet stores. If the water parameters are outside of the safe range, this indicates poor water quality. Poor water quality means that something has gone wrong in the process of the nitrogen cycle (over feeding, deceased fish, waste buildup, unclean filter, water not changed enough), and puts the fish at risk of disease and possible death.

‘Nitrifying bacteria’, referred to as “good bacteria” helps the nitrogen cycle occur. It takes up to six weeks for the levels of bacteria to stabilise. Plants also use the nitrates in the water. During the settling in time tanks should be tested each day for ammonia and nitrite

This settling in period can be handled in a few ways as detailed below.

Options 1 and 2 – after you have introduced the fish:

  1. Regular water changes. Change about a quarter of the water every week whether it is dirty or not. Be very careful to ensure that the appropriate replacement water is at the same temperature as the tank (to within two degrees). Always add dechlorinator or conditioning salts to the water whenever you do a water change. If the tank is particularly dirty replace about 1/3 of the water at once, clean the filter and then remove and replace a quarter of the water each day until it is clear again. Carefully monitor the ammonia and nitrite levels.
  2. Commercially available bottles of ‘nitrifying bacteria,’ as these will convert the toxic ammonia and nitrites to the less toxic nitrates.
    Option 3 – before you have introduced the fish
  3. Fishless cycling – involves the addition of ammonium compounds to a tank containing no fish to enable the ‘nitrifying bacteria’ to develop before any fish are added.

Throughout the time you have the fish tank, it will require on-going maintenance. This means that the tank will require a weekly 20-30% water change, and regular filter cleaning and maintenance, as described above. A siphone can be purchased from a pet store. Siphons allow gravel to be circulated at the bottom of the tank, to remove fish and food waste. This removes water in the process, and is an easy way to remove the water necessary for a water change. Fresh water, dechlorinator and good bacteria can then be added to the tank again. Please refer to a reputable Aquarium Hobbyist Group for information on maintaining marine fish tanks.

Establishing an outdoor pond

Fish ponds are best if in-ground and made of cast concrete, although some prefabricated cement constructions and some butyl rubber liners are suitable. Where plastics are used, ensure that the supplier warrants them suitable for use with live fish, as many plastics are toxic. The minimum depth of available water must be 30 cm, but it is wise to have even deeper sections so that fish can reach cooler water areas. As with aquarium fish, the number placed in a pond will depend on the surface area of the water and whether or not the water is filtered and circulated. Please check with your local council for any relevant regulations regarding fish pond installation, construction and depth.

Adequate aquatic plants must be placed in the pond to help remove nitrates and phosphates (which cause algal growth) and to provide shelter for the fish and a place for eggs to be laid. Pond set-ups requires a pond pump, taking water in near the bottom of the pond, and pumping it out again near the top of the water, to agitate the surface and aerate the water. A good general rule for the size of the pump required, is that the pump should be able to move around half of the total pond volume of water every hour.

Algae and plants generate oxygen during the day, but absorb oxygen at night. On still warm summer nights the plants and algae can easily remove all of the oxygen and kill the fish. To avoid this, ensure that the pond pumpruns continuously at night when there is no wind to ruffle the water. Rocks must also be strategically placed to provide good shelter, enrichment and for decorative purposes.

Ponds are best situated out of direct sunlight in order to control algae growth. Watch for predator birds if setting a pond near large trees. A water filter system is essential to remove algae and other impurities and the system should be designed so that one-quarter of the water is replaced each week. Newly poured concrete ponds, and new butyl rubber liners should be filled with water and allowed to stand, with the pump and filter running, for four weeks. After draining and cleaning it is safe to refill and stock with fish.

Introducing New Fish

When you first bring your pet fish home, they should be introduced to the tank slowly. Place the bag from the pet store into the tank and allow it to float there without undoing the top. Leave it to float for at least 15-20 minutes, to allow the temperature of the water in the bag to equalise with the temperature of the tank water.

Next, undo the elastic band at the top of the bag, and slowly allow a little of the tank water to enter the fish bag. Over the next 5-10 minutes, do this repeatedly, until much of the water in the fish bag has been replaced by tank water.

Once this has occurred, you can slowly tilt the fish bag into the tank, so that the fish can gently swim out into the tank.

If introducing a new fish into an already establish tank, it is important to place the new fish into a quarantine tank first. A quarantine tank is a completely separate tank that has been cycled, but contains no other fish. Place a new fish into for at least 7 days, before introduction to the main tank. The aim of this is to reduce the risk of disease being introduced into an already established aquarium. While it may not be enough to completely eliminate every disease, a minimum of 7 days is often enough time for external parasites or other diseases to begin to show symptoms, following the stress of being moved from the pet store or previous tank. Once the new fish has been quarantined and appears visually healthy, they can then be moved into the primary aquarium, following the same process as above.

The same process of introduction and/or quarantine should also be undertaken for fish being introduced into a fish pond.


Never overfeed the fish. If your fish are kept at a constant temperature in the aquarium you can generally feed them once per day. Allow just enough food for the fish to feed for about two to three minutes. Do not give so much that there is left-over food in the tank, as this will soil the water.

Dietary requirements depend on the species of fish. As a general rule, a good quality pelleted diet, specific to the species of fish being kept, should be fed as the basis of the diet. This can then be supplemented with food appropriate to the species, potentially including brine shrimp, glass shrimp, smaller feeder fish, algae flakes and pellets.

Any uneaten food should be removed immediately, either from the surface or siphoned off the tank floor. If uneaten food is not removed, this will break down into waste matter, causing a build-up of toxic ammonia in the tank. This damages the water quality and risks the health of the fish.
Pond fish require feeding every two days in summer and once weekly in winter.  Good quality, species appropriate pellets should be fed as the primary diet.


The principal causes of death of fish in an aquarium or pond are overstocking and polluted water. Both of these result in an increase in ammonia level, a decrease in pH level, and poor water quality. As fish must live permanently in the area where they eat and excrete, the tank must be cleaned regularly to remove this material, which will foul the water. Learn to recognise normal fish behaviour, and know what to do if the fish begin to behave in an unusual way. For example, fish gasping on the surface is a sure indication of a fouled tank or pond with little oxygen left. Other signs of infections and diseases are change of colour, swollen skin or eyes, a swollen belly, a rotting tail or white spots over the body of the fish. Check with your veterinarian for advice.

Some remedies for common fish diseases are available in aquarium stores, however it is always best to check with a knowledgeable veterinarian, to accurately identify the disease and the cause, prior to administering treatment. Prevention is always better than cure, and maintaining good water quality through regular cleaning and tank/pond maintenance is the best prevention.

If a fish does become sick, it is best to  remove it to a small, separate “hospital” tank, and consult with a knowledgeable fish veterinarian. While some products for common fish problems are available from aquarium shops, it is important to ensure the correct disease is identified. Many fish diseases are a result of poor husbandry or tank/water maintenance. Water sampling and testing is often important in determining the underlying cause of fish disease. Correcting any underlying problem is essential to maintaining the health and wellbeing of all the fish in the tank. Separating unwell fish from healthy pets can help prevent others becoming is best to remove it to a small treatment tank so that the other fish do not become infected. It is a good idea to have a small spare tank that can be used as a treatment tank if required.

Remember that tobacco, dog and cat flea treatments and garden and household sprays such as insecticide can pollute the aquarium or pond and kill the fish. Read the labels carefully and seek advice. Always cover the tank or pond before spraying and turn off any aerators. Equipment used for tank cleaning and maintenance should be clearly labelled and only ever used for the aquarium, so that there is no risk of contamination from other substances.

Looking to learn some new skills?

Want to learn more about animal care and welfare?

Read more about our Education courses today.

More Details

Need some goodies for your pets?

Profits from our online store go straight to helping animals in need.

Your purchase makes a bigger difference than you think. 💖

Shop now