Fish — Aquariums — Environment


Aquariums must provide sufficient space and amount of water for fish depending on the size, number of fish and type of aquarium. Fish must have adequate space to swim around and participate in normal behaviours. The aquariums must also be able to hold an ample amount of water and be located in an appropriate position in the room.

    • 4.5 litres of water per 1.5cms of fish must be provided as a minimum water requirement (more space required if not ventilated)
    • 1-2 aerators to be used per 35-75litres of water
    • Suitable covers must be used on tanks
    • Water must be suitably conditioned prior to use with all chemicals and residues removed
    • Water pH must be suitable for fish
    • Water temperature must be suitable for the species of fish, for temperate and tropical fish 22-25oC is suitable
    • A high level of hygiene and cleanliness must be kept at all times
    • Tanks must not be exposed to direct sunlight
    • Natural environment should be replicated in the tank
    • Normal diurnal pattern of lighting must be provided
    • Air surrounding aquariums must be of acceptable quality with respect to dust, chemicals and smells with special care taken when using insecticidal sprays.

The least complicated environment is a natural pond in the school grounds, however it must be noted that only some species of fish can be kept in these conditions. If this is not possible, an aquarium in the classroom is relatively simple to maintain. The tank needs to be kept at room temperature and should not be exposed to direct sunlight, as the sunlight will overheat the water and cause a rapid growth of algae.

The tank should include plants and other invertebrates, and be allowed to stabilise for one to two weeks before the fish are added. Filtration and aeration can be added to facilitate fish survival but each addition of physical support to the tank increases the probability of the system breaking down. It also adds to the amount of monitoring required. If tropical fish are to be kept, a heating and temperature control system must be used.

With a marine tank, the system becomes even more complex and is not recommended unless you have prior experience and success in another context such as at home.

The following points are general rules for preparing freshwater aquaria suitable for tropical and temperate fish species, including Australian native fish.

When adding the fish to the tank, float the bag in the aquarium for at least 10 minutes to allow the fish to acclimatise to the new water temperature. Then open the bag and slowly add small amount of tank water to the bag over the next 15 minutes. After this has been carried out, the fish can then be netted from the bag and released into the tank.



The aquarium should not be exposed to direct sunlight as the sunlight will overheat the water and cause a rapid growth of algae. A diffused, filtered natural light can be used. If using artificial light, fluorescent tubes can be used for almost all aquariums. A timer must control the amount of light. Lights must not be suddenly turned on and off because some fish may become very nervous and move erratically around the tank. A dimmer light switch will avoid this problem. The correct lighting is very important for aquarium plants. In a new aquarium, 12 hours of artificial lighting each day should be enough for most aquatic plants. The exposure time may be increased or decreased until a good plant growth rate is achieved.



An aquarium should try to replicate the natural environment of the fish. This can be achieved by provide aquatic plants, objects for hiding and exploring like rocks and hollow pipes and logs. Rocky overhangs can also provide fish with areas of shelter and privacy which is essential their wellbeing and reduces stress when being observed.



Washed river gravel is ideal as a bedding. Gravel used must be clean and free from chemical residue. The bottom of the tank should be covered with an average of 75mm.



This process has a very significant effect on the water quality and fish health. The three types of filtration are mechanical, biological and chemical. The most popular and easiest to apply is mechanical filtration. This is recommended to improve fish health and survival.



Water should be changed about once every one to two months. It is important not to replace all the water at once, 20–25% of the volume is sufficient. A major cleaning should be undertaken once every four months. The fish must be removed, placed in a container with 25% of the original tank water and covered. The walls of the tank must be cleaned carefully, with all chemical residue from the cleaning being rinsed away. Thoroughly wash sand and gravel to remove any accumulated debris. The tank should be two-thirds filled with tap water and allowed to stand for at least half a day before the remaining sand or gravel, water and fish are returned to the tank. Water is aged by leaving it stand for 24 hours or by using a chemical ageing agent. Ensure that the aging process has been carried out prior to beginning tank cleaning. Have the aged water ready to place into the clean tank.



Details about breeding tanks vary with each species. Separate breeding tanks may be required.