4. Once past the cormorants, the fish must avoid the boat anglers. Fish must make four trips back and forth across the deep river pool, and collect a food token from the sideline area during each pass. Only one token can be picked up at a time! If an angler catches a fish with only one food token, he or she must let the fish go. Anglers can only “catch” fish that have 2-4 food tokens. A capture must be with both hands. If an angler catches a fish, he or she should leave the boat and take the fish to the top of the fish ladder.
5. At some random point (the teacher’s discretion), the whistle is blown. Action freezes. It is announced that it is now the middle of summer, and oxygen in the lake is depleting. Any fish that has fewer than three food tokens is dead. These dead fish come to the top of the fish ladder.
6. The simulation resumes with the remaining fish picking up food tokens, avoiding the anglers, and going to the place where they can start up the fish ladder. They must also avoid the grasp of the shore anglers. These people are restricted in the area from which they can work, but the funnel made of boundary markers is intentionally close to them so that they can reach out and tag fish. A two-handed grab is not necessary, but the shore angler must take the caught fish to the top of the fish ladder.
7. Fish who make it past the shore anglers ‘climb’ the fish ladder by carefully stepping over the backs of their classmates. Those who make it to the holding pool at the top of the fish ladder are the successful breeders.
8. The activity ends when all the fish are gone before the holding pool is reached, or when all the surviving fish reach the holding pool.
9. Engage the students in a discussion. Explore such issues as:
>the apparent survival/mortality ratio of fish
>the role of the predatory wildlife and anglers
>what the consequences would be if all the juveniles that began the journey made it successfully and
>what seemed realistic about the simulation and what did not
>Ask the students to summarise what they have learned about the life cycle of fish and their limiting factors. Make sure the students have a clear, working definition of limiting factors. Encourage the students to make the generalisation that all animals, not just fish, are affected by limiting factors. Have them give examples.
Be sure the aquarium has some variety of habitats: plants, rocks, hiding places, open areas, light and dark backgrounds, covered or partly enclosed spaces.
Fasten the clear plastic sheet to the outside of the largest side of the aquarium. Using a marking pen draw a grid of rows and columns so the location of individual fish can be described easily. You may wish to describe boundaries for front and back of the aquarium too.
Have the students identify and name all the individual fish. Be sure each student can recognise the different individuals.
An obstacle to fish migrations. Weir on the Macquarie River near Warren, NSW. Photograph: Bill Phillips
Southern Purple Spotted Gudgeon. Photograph: Gunther Schmida
Divide students into pairs or small groups. Each group of students should watch ONE FISH for 3-5 minutes at a time, recording the location of the fish on one of the Fish Tank Territories Observation Data Sheets (see below) every 10-20 seconds. Each group should choose a fish to focus on, making sure several different fish are included in the study.
After observing the same fish daily for 3-4 days, students should have baseline data on normal patterns of space use for each fish. Have students discuss results so far and describe how each fish uses the available habitats.
Students should then change ONE factor in the habitat. They could move an existing thing (plant, rock, etc.) or add something new to the tank. Before making the change, students should predict how the change might influence the behaviour of each fish.
As soon as the habitat is changed, the group should observe their fish again. Students should determine whether the fish changed its behaviour in response to the new configuration in its habitat.
Observations using these same conditions should be made for 3-4 days. Changes can be made one at a time, with students recording observations about their effects over the course of a few days.
Groups should report their results to the class. The class should then draw conclusions about the ways fish use habitats in the class aquarium.
Reports presented to the class
Each group will create a poster, graphs, or other display to illustrate their results. Each student will hand in individual observation sheets and contribute to the group report.
Extension - alternative to live fish tank
Get the students to create their own drawing art version or fabric fish with different materials. Use this to highlight some key features of each species – native or introduced.
FISH TANK SETUP GUIDE – CREATING A NEW HOME FOR NATIVE FISH IN THE CLASSROOM
Preparing for your project
Some planning will be necessary to ensure the success of your project. The following subjects should be given some consideration before starting.
Species of native fish
Australian native fish for aquarium use are often available through your pet shop. As well, you will often see fingerlings of larger species such as Murray cod, Golden perch and Southern pygmy perch in aquarium shops. If you purchase any of the latter species, remember that some of these fish grow to a large size and unless you have a suitably sized aquarium they may not be for you. A reputable aquarium shop should be able to advise you of the requirements of any fish you intend to purchase.
If you decide to try and catch your own fish (this may not be easy!) you must first seek advice from the local wildlife or fisheries management agency as in all States and the ACT certain species are protected and cannot be taken from the wild. You should also get advice on how to dispose of the fish after your exercise is completed. Again, there are different rules and regulations operating in some States.
It is advisable to request permission from any land owners on whose property your intended collection site(s) may be found. It is only common courtesy to do so, and may make all the difference between gaining access to the site and being asked to leave!
The size, numbers, and needs of the fish you wish to keep will dictate the size of the aquarium you will need. Conversely, space and resource restrictions may limit the tank size you are able to have, which will be the deciding factor for the species and numbers of fish available for your project.
An ideal tank size for the classroom is between 75 and 120 litres. These sizes allow for a variety of species to be kept without requiring too much maintenance from those involved. They are also small enough to make finding a suitable tank location relatively easy.
Equipment and supplies
There are several items besides the tank that you will need to properly maintain your aquarium. They are:
Hood with fluorescent lighting
Many native fish are quite adept at jumping out of aquariums. Therefore, a hood that covers the entirety of the tank is a necessity. Many commercial hoods come with a lighting system. Avoid the incandescent lights as these may heat up the tank’s water and provide little aid to live plants should you choose to keep them. On the other hand, fluorescent lights last longer, have little to no effect on the water temperature, bring out the fishes’ natural coloration, and use less energy. Wide-spectrum fluorescent bulbs may also be purchased that will help aquatic plants photosynthesize.
There are many types of filters available on the market that will keep your aquarium’s water healthy for the fish. Filters can be broadly classified in two categories: biological and mechanical.
Biological filters, such as sponge and under gravel filters, rely on using the natural aquatic cycle to keep the water clean. Mechanical filters draw the water out of the tank and filter it through several media, keeping the water clean by removing small particles and chemical treatments.
Experts suggest you use a mechanical filter, such as one from the Marineland Penguin or Emperor series. These relatively quiet filters hang on the back of the aquarium, and require no more maintenance than occasionally having to replace a filter cartridge. Some mechanical filters have a feature called a bio-wheel. A bio-wheel adds effective biological filtration to any filter’s capabilities, thus combining the best of both worlds.
A thermometer, whether it’s the kind that sits in the water or adheres to the outside of the tank, will provide accurate, up to date information about your tank’s water temperature. Most native fish are able to withstand a wide range of temperatures, preferring the water to be in the lower to mid 20’s Celcius.
Feeding your fish a variety of food is crucial to maintaining their health and coloration. Many foods are commercially available in dry, freeze-dried, and frozen forms. It is best to switch regular fish feedings between frozen and dry foods, with regular supplements of fresh foods (i.e. live worms, insects, shrimp, fish or fish meat, etc.) to the diet.
Cleaning gear should consist of a clean bucket used only for aquarium maintenance, a gravel vacuum with siphon hose, and some sort of algae scraper. Never use detergents or chemicals to clean your aquarium!
Substrate and decorations
A properly decorated aquarium will contribute to the fishes’ health and add to the overall beauty of the aquarium. The right combination of gravel, rocks, and plants will make your new fish feel right at home, and can be manipulated to imitate your local water systems. Care should be taken to avoid brightly coloured or fluorescent gravel and objects. These colours are not usually found in the fishes’ natural habitat and may cause them undue stress. Realistic plastic plants are available in many sizes and shapes should you choose not to keep live ones. When decorating with rocks, make sure they are free of sharp edges and metals. A good source for natural gravel is the landscaping section of your local hardware store.
Water purifier chemicals
Most of us do not have easy access to clean natural water sources. Therefore, most aquariums are filled with tap water that may contain several additives, such as chlorine and chloramine, that are unhealthy for fish. These chemicals can be removed with inexpensive aquarium water treatments that are readily available at most pet stores and aquarium product suppliers.
There may be times when you need to temporarily or permanently remove one or more fish from your tank. Chances are high that you will not be able to catch them with your bare hands. Again, pet stores normally carry a variety of inexpensive nets that you will find suitable for your aquarium.
Where you place your tank can have a great effect on its continued success. Away from direct sunlight is best to avoid temperature fluctuations and severe algal growth. Also, avoid locations where overly curious or boisterous children can cause harm to themselves, the tank, or both.
An established aquarium will require several easy, regular maintenance steps to ensure the health of the fish. These steps can be broken into the following categories:
Once per day, the fish should be fed all they can eat over a 5 to 10 minute period, ensuring all the fish are eating. Care must be taken to avoid over-feeding, as the build-up of uneaten food can quickly pollute the water. A minute or two should be taken to observe the fish (for any signs of distress or disease) and the tank (for external problems, temperature changes, etc.). Early detection can go a long way in problem solving.
Check the filter(s) for possible cleaning. Do not rinse filter cartridges and other filter media in chlorinated water, as beneficial bacteria may be killed off.
Although today’s filters are excellent for maintaining proper water conditions, they are still unable to remove everything from the aquarium. Solid waste will gradually accumulate in the gravel, as will chemical waste levels in the water. Thus, it is best to do a 25% water change, using a gravel vacuum and a 20 litre bucket, once a month. Never change all of the water at once, as such a dramatic change in water chemistry can shock and kill the fish. When adding new water, try to get it as close as possible to the temperature of the remaining tank water and add the appropriate amount of purifier to remove unwanted chemicals.
Setting up your aquarium
When done correctly, tank setup can be a relatively fun and hassle-free process. The following steps provide a general guideline for tank setup that is adhered to by most aquarium hobbyists.
1. Make sure the inside surface of the aquarium and all objects that will come into contact with the water are thoroughly cleaned. NEVER use detergents or other cleaning chemicals for this purpose! Hot water and untreated scrubbing pads should suffice. Gravel can be rinsed through common kitchen strainers or inside buckets.
2. Check to ensure the tank is sitting squarely and securely on the surface it is to be kept on, then add cleaned gravel. If an under gravel filter is to be used, be sure to place it on the bottom of the tank prior to adding the gravel.
3. Fill the tank about half way with water. Once done, add decorations, such as larger rocks and driftwood, that will not be disturbed by adding the remaining water. Once the tank is filled, add the remaining decorations.
4. Add hood, filtering and other equipment you may have. Once the tank is set up, turn on all the equipment and let it run as if the tank already had fish. Check everything occasionally to make sure it is running properly.
5. No matter how much you rinse the gravel, the newly filled tank will be cloudy for several days. Chlorine and chloramine will also remain in the water for up to 48 hours before dissipating completely. Allow the tank to run like this until the water clears. When it does, it is ready for fish.
Stocking your aquarium
Inside all aquariums, just as in all rivers and lakes, there is a continuous biological cycle that works to keep the water clean. Basically, several types of bacteria break down pollutants such as fish waste and other decomposing material into harmless chemicals.
In an aquarium, the bacteria feeds on the fishes’ waste and uneaten food, and in the process keep the water clean enough for the fish to live in. How well this cycle works depends largely in maintaining a balance between the number of fish and the amount of water necessary to support the bacteria that will clean up after them.
When a tank is first set up, there are no bacteria to clean the water. As the first fish are added, the amount of their waste products and uneaten food in the water will begin to rise unchecked. Fortunately, the necessary bacteria will soon begin to grow and filter the water. This process, called cycling, may take up to 4 weeks to completion. If too many fish are added to an aquarium at one time, their waste levels may build up faster than the bacteria can grow to handle the load. Such a situation may lead to the death of some or all of the fish.
Therefore, it is best to add only a few fish at a time. Two or three smaller fish per 40 litres of water are usually enough to get the cycle going. Once the tank has gone through its initial cycle, it will be ready for the addition of more inhabitants. Each addition of new fish will cause another bout of cycling to occur, but with the established base of initial bacteria, the new cycles will take less time to reach completion.