Set up a freshwater aquarium

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How to Set Up a Freshwater Aquarium

First Things First

  • Read through all of the directions below before starting.
  • Determine what size aquarium you will have.
  • Determine where you will place the aquarium. Make sure it is set up on a sturdy table away from any place where it would often be bumped. Also remember that unless you have an algae-eater or some snails in the tank, algae will grow in abundance if the tank is placed in direct sunlight.
  • Purchase or locate the necessary materials to keep the tank clean and the fish healthy.
    • under-gravel filter
    • food
    • gravel and rocks||tank scrubber
    • air pump and plastic tubing
    • dip net
    • gravel and rocks
    • tank scrubber
    • plants
    • water quality test kit

Setting up the Aquarium

Below: This drawing shows how water circulates through an undergravel filtration system. The 'driving force' for the movement in this basic set-up is provided by air from an electric pump. The rising air bubbles in the uplift tube cause an upward flow of water that in turn 'pulls' water from underneath the filter plate across the whole base of the tank. As long as the pump is working the circulation continues. If you position the air pump ash shown here it is advisable to fit a non-return valve in the airline to prevent water siphoning out of the tank if the pump stops.


Filter/Air Pump

The best all around filter is the undergravel filter. It is essentially a piece of plastic with small holes or slots in it. In one corner is a large round hole where a plastic "uplift" tube fits. An air pump and tubes are connected to the uplift tube. The installation of this type of filter is explained below.

Place the filter on the bottom of the empty tank. (They are available at stores in standard sizes to fit a wide range of tank sizes. For larger tanks, you can fit more than one filter plate as necessary.) The best arrangement places the holes for the uplift tubes in the rear corners where they can be hidden from view with rocks or plants. Set up the uplift tube(s) and attach clear plastic tubing and an air pump (both of which can be obtained at a pet store, or K-Mart/Wallmart/etc.).



Aquarium gravel is the best substrate for your tank, however other substrates can be used. Avoid gravel used for building purposes as it may have stones which are not suitable for tank use. Also avoid sand, as the grains will clog together and stop water from flowing through the filter. Regardless of the substrate used, before putting it in, be sure to wash it very thoroughly (without soap) until the water running away from it is clear. Cover the filter plate with a gravel layer about 2-3 inches deep.


You can now decorate your tank. Rocks make a good background for fish, however not all rocks are suitable. Generally, rocks with lines or veins of metal in them are unsuitable as they affect water chemistry. You can test any rock you get with a few drops of vinegar. If the vinegar dropped on the rock fizzles vigorously then the rock contains calcium compounds that will make the water harder and more alkaline than most fish can tolerate. Don't worry too much if a few little bubbles appear, as most rocks have some small calcium deposits. When you have picked your rocks, soak them for a week in a bucket of water to remove acids and leach out any other impurities.

Before putting the rocks in the tank, slope the gravel from front to back so that it is twice as deep in the back as the front. This allows any debris to accumulate at the front where it is easier to remove and also provides a firm base for embedding rocks and other decorations. Make sure the rocks you put in cannot fall on top of the fish.



Ordinary tap water is fine for filling up the aquarium as long as you let it sit for several days before adding fish (the chlorine in the tap water will kill the fish). There are dechlorination solutions you can purchase at your local pet shop. Several drops of the solution in pure tap water is usually enough to dechlorinate the water instantly.

When adding water to the aquarium for the first time, add water that feels cool to the touch, but not cold. Trickle the water in slowly so that you do not disturb the gravel. Pouring water onto a rock will reduce the impact of the flow. Continue adding water until the level is about 1 inch from the top of the tank. It is a good idea to let the filter run for a week before adding fish to the tank.


Plants also make a nice addition to any aquarium, although they are not necessary. Plastic plants are by far the easiest to use. They are often almost indistinguishable from real plants, do not die, do not overgrow the tank, will not be eaten up by fish or snails, and last forever. However, real plants can certainly be used. There are a large variety to choose from at your local fish store. Ask your dealer how to care for them.


Different kinds of fish can often live together, but care must be taken in choosing the right community of fish for your tank. It is good to pick fish that will utilize different areas of the tank. Some fish are bottom-dwellers, some are mid-water swimmers, while others prefer to stay near the top. A mixture of these will make a nice balance. Also, be sure not to put a carnivorous fish in with a lot of little fish, unless you want to end up with one big fish!

How many fish can you keep in your tank? That depends mainly on the amount of water surface area, as fish breath oxygen that is mainly absorbed into the aquarium through the water surface. To determine roughly how many fish your tank can hold, first multiply the length of the top two edges together to give you the surface area of your tank (length x width). You should aim to have no more than 1 inch of fish for every 10 square inches of surface area. For example, a tank that measures 36 x 15 inches has a water surface area of 540 square inches. Dividing 540 by 10 produces a total recommended fish length of 54 inches. Thus, you could keep nine fish 6 inches long, or 18 fish just 3 inches long.

Once you have the fish, you will need to acclimatize them. The water in your tank is likely to be a different temperature than in the bag or pail of water you have the fish in. It is best to put the fish in a closed plastic bag with enough water that they have been in to cover them and a good pocket of air trapped at the top to keep the water oxygenated. Float the bag in the tank for 10-15 minutes. After this period, open the bag carefully, and with a small cup, pour some water from the tank into the bag. Wait another 5 minutes and then gently release the fish into the tank. If possible, add newcomers to the tank gradually, over the course of several days or weeks, in order to allow the filter system to establish itself and break down the wastes the fish produce.

What to do Next

Feeding Fish

Fish should be fed 2 to 3 times a day with very small helpings. A good rule of thumb is that the fish should eat everything you give them within 3 to 5 minutes, or you are feeding them too much. A fish is not harmed if it has to "fast" once or twice a week. This often improves the appetite and does not harm the fish. In their natural state, they can go weeks without food.

Aquarium fish will eat almost anything (flakes, pellets, live foods such as Daphnia or Tubifex worms, and even other fish). It is important that the fish like the food and that the pieces are small enough to be eaten. It does not good to feed a big fish flakes or a little fish large lumps of food. You should simple try to provide a varied diet of nutritious (full of vitamins and nutrients) food that is the proper size for the fish you are feeding. A large variety of fish food types can be found at your local fish store.

Maintaining Your Aquarium

Scouring pads on long handles such as this one, make cleaning the inside glass of the aquarium relatively easy, at least in fairly small tanks.

It is very important to maintain water quality in your tank. If your filtration system is working properly, there should be few problems. However, to be certain that nitrite does not build up in the tank, regular water changes are vital. A water change should be at least 10 to 15% of the water in your tank. Simply scoop or siphon out 10-15% of the water in the tank and replace it with new (dechlorinated) water at least every other week. Remember to get the temperature of the new water as close to the tank water temperature as possible before adding it to the tank. Pour the water in slowly so that it does not disturb the bottom of the tank and upset the fish.

Below: Scouring pads on long handles such as this one, make cleaning the inside glass of the aquarium relatively easy, at least in fairly small tanks.

Other jobs that should be done include:

  • removing any algae growth on the sides of the tank (a scouring pad on the end of a long handle or stick works well).
  • trimming or replanting live plants.
  • watching the fish for five minutes every day to check for signs of disease or odd behavior.
  • checking the water temperature, and other physical parameters. Test kits are available to test nitrite, pH, and the hardness of the water in your tank. Fish live best within certain parameters which can be monitored by testing.

Fish Health

Fish will always show symptoms of disease at an early stage. Signs to look for include fish holding their fins tightly clamped to the body, fish swimming with the head near to the surface all the time, fish swimming with the head up or down, loss of color, ragged fins, scales sticking out or dropping off, and a general loss of appetite and condition.

Stress is the most common cause of fish disease. Fish can be stressed in many ways. Tapping on the glass, allowing temperatures to rise and fall, having a poor mixture of fish in which one or two are bullies and the others are bullied, all contribute to the stress. Anything you can do to alleviate these problems will decrease the incidence of disease in your tank. Other Important Things You Should Know

  • Never use soap or detergent to clean an empty aquarium; rinse with warm salty water instead.
  • never move a tank with water in it. The sloshing water may put excessive strain on the seals and cause the tank to spring a leak.