Introduction to Freshwater Fish
A well-set-up tank that is functioning properly will require only a minimal amount of time spent on its maintenance. The aquarium should develop into a stable ecosystem, in which toxin levels are kept in check as part of the natural cycle. With regular checks and a few simple “housekeeping” tasks, such as partial water changes, your aquarium will look its best and your fish will stay healthy and content.
Regular partial water changes ensure that toxic chemicals do not build up in the tank and harm the fish. They should be carried out once a month or when indicated by water test results. Start by turning off the power to the tank. Fill a length of siphon tube (see box, opposite) with tap water, adding a drop of water conditioner to dechlorinate it, just in case any should escape into the tank. With a finger over each end of the tube, place one end in the tank and the other into a bucket. Release the tank finger first, followed by the finger in the bucket; water should flow from the tank into the bucket.
A gravel cleaner can be attached to the end of the siphon tube; as you move the cleaner over the substrate, the water flow stirs up the gravel and sucks out particulate waste. When you have removed enough water, simply lift the tube out of the tank. Before refilling the tank, add a suitable amount of water conditioner to the fresh water, and make sure that it is at the same temperature as that within the tank, or the fish will be stressed by the sudden change. Pour the water in slowly, taking care not to disturb the roots of the substrate plants.
If your tank has a biological filter, switch the power back on as soon as possible, because the aerobic bacteria that provide the basis for filtration will die if they do not receive oxygenated water for some time. Should you need to replace the filter sponge, be sure to add a seed culture of bacteria. Be prepared for an initial deterioration in water quality, since the biological filter will not work efficiently again until the bacteria have colonized the surface of the new filter sponge.
Problems with algae
Excessive algal growth may occur if the aquarium lights are left on for too long. It is especially likely if there are no plants in the tank, or if the plants in a new tank are not yet fully established, because plants naturally compete with algae for nitrates and other key growth compounds in the water.
Without competition, algae spread more easily, not only growing on the glass but also covering rockwork and other tank decor. Reducing the length of time that the aquarium lights are on will help to curb this problem, as will making regular partial water changes (which keep the nitrate levels low) and introducing fish that browse on algae.
Monitoring water quality
Test kits and meters (see p.46) should be used to make weekly checks on the water quality. Daily visual checks are also vital; any unexpected change in the appearance or behavior of your fish may indicate that there is a problem. For example, if the gills of a fish become brown instead of the normal pink, it is likely that there is too much nitrite in the water. This will interfere with the ability of red blood cells to carry oxygen.
Regular partial water changes will usually cure nitrate excess. A rise in the level of nitrite or toxic ammonia may be due to “new tank syndrome” (see right), caused by overfeeding on a regular basis, or a result of overstocking the tank, which places extra demands on the filtration system.
Fish differ in their susceptibilities to dissolved chemicals, which is often a reflection of their habitat in the wild. Those occurring in fast-flowing water where there is little opportunity for pollutants to accumulate, such as discus (see pp.142–143), are much more vulnerable than those that naturally inhabit small ponds. Discus show obvious signs of nitrite poisoning when this chemical is present in concentrations of just 0.5 mg/liter, whereas most other fish will be unaffected until the level rises to 10–20 mg/liter. Ammonia can be removed by the chemical zeolite, which is either added to the filter (if present) or simply dropped into the water.
REGULAR MAINTENANCE TASKS
- Check the thermometer; if the water temperature has changed, the heater or the thermostat may be faulty.
- When feeding the fish, watch out for any decline in appetite, since this is usually a sign of illness.
- Check the lights above the tank; replace a burned-out tube without delay.
- Make sure the filter is working effectively; if it is not, there may be a blockage in the system or even a power failure.
- Reposition any substrate plants that have become uprooted and floated to the surface.
- Carry out water tests to monitor levels of nitrogenous waste. Keep a check on the pH as well, using either test kits or a meter.
- In a newly established aquarium, carry out a partial water change of up to 20 percent every week, since the filtration system will not yet be fully functional.
- Check for any change in the appearance or behavior of the fish that may indicate that they will soon be breeding.
- Siphon out any mulm accumulating on the substrate. This will reduce the burden on the filtration system.
- Carry out a partial water change— approximately 25 percent of the functional tank volume—using a gravel cleaner as well.
- Trim dead stalks and leaves from plants. Add aquarium plant fertilizer to the water.
- Remove any buildup of algae in the tank by cleaning, and then adjust the period of light exposure within the aquarium.
- Where an internal power filter or an external filter are being used, strip down, check, and clean the filtration system.
PARTIAL WATER CHANGE
Cleaning the gravel while siphoning water from the tank improves the filter’s efficiency and ensures that the gravel bed does not become compacted. Save the tank water that you siphon into the bucket; you will need this to rinse the filter sponge.
Cleaning the filter sponge Rinse out the sponge in water taken from the tank, to remove any debris that has collected.
Siphon out the water
- Place the bucket below the tank to ensure a good flow. Never suck water through the tube to start the flow—you could swallow harmful microbes.
Clean the gravel
- Take care not to uproot any substrate plants when using a gravel cleaner. The water flow will not be strong enough to suck gravel up the tube.
NEW TANK SYNDROME
Water conditions in a new tank take time to stabilize. There is an initial rise in the level of ammonia, which the fish excrete as waste. As the biological filter starts to work, beneficial bacteria break down the ammonia into slightly less harmful nitrite, which is eventually converted into nitrate. Although this is called new tank syndrome, a similar situation can arise in a mature tank if the filter’s efficiency is dramatically reduced. This could be caused by the use of antibiotics (which will kill the bacteria), a breakdown in the oxygenation of the filter bed, which is essential for the survival of these aerobic microbes, or simply the replacement of the filter sponge.
The rapid initial peaks of ammonia and nitrite in a new tank are followed by a slower climb in the nitrate level. It takes about seven weeks for a biological filter to become fully functional.
- Arrange for a friend or neighbor to check the tank every day in case there is a power failure or any of the equipment malfunctions.
- If someone else is to feed the fish, show them exactly how much food they should give each time in order to prevent overfeeding.
- As an alternative, consider using an automatic feeder or a food block.
- Carry out a partial water change and check all the equipment before you leave.
- Leave a contact number in case of emergencies.