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How to Set up a Tropical Freshwater Aquarium

Aquariums are a lovely addition to any space, creating a lively focal point and a source of color and entertainment. Read below the jump to learn the steps involved in setting up a tropical freshwater aquarium. You'll be pleased with the process as well as the end result, and finish with a new 'water world' of your own.


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    Before you get your aquarium, choose a place to put it. Remember that wherever you place it needs to be able to support the weight of the aquarium.
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    Bear in mind the temperature of the location.
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    Set your aquarium up. Place it securely in its new home, and if possible check to make sure it is level. Remember, unless it is a very small tank, once it is full you should never attempt to move it. Moving a tank with water in it can lead to disaster.
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    Rinse your gravel/substrate. If you plan on using live plants, consider researching what substrate is best to use. Remember, some fish have specific requirements on what substrate/gravel they need. You will need approximately 250g of gravel per liter of tank (depending on your setup). It is important to have enough gravel as gravel is a place for good bacteria to grow on(more on those later). You will want to rinse your gravel well before placing it in a tank to remove dust and debris from travel. If you are using an undergravel filtration system install this now. Scoop the gravel into your tank slowly so you do not damage or scratch the glass. Generally it is best to create a gentle slope of gravel; deepest in the back and most shallow in the front.
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    Water time! Place a small, clean dish on the gravel floor of the aquarium, and pour water into this dish if you wish to avoid displacing the gravel. If you are a beginner fish keeper, it will be easiest for you to use tap water.
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    Add de-chlorinator (a liquid that will render your tap water safe for fish to live in it, it removes the chlorine. Good brands will also remove chlorine, ammonia, and nitrite). Be sure to follow the instructions on the package.
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    Add your decorations. Remember to use only safe decor for a freshwater aquarium. Not all rock types are safe for freshwater aquariums- research or ask your local fish shop what their recommendation is. Consider what species you are going to keep- décor for an aquarium full of African Cichlids would be different than for goldfish, for example.
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    Attach your filter. Each filter is different so be sure to follow instructions. Once it is hooked up properly, you may plug it in and ensure that it operates properly. If you are using a canister style filter, consider attaching the spray bar so that it agitates (creates ripples) on the surface of the water. This will help dissolve oxygen for your fish. All other types of filters should normally agitate the water.
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    Place your heater into the tank. Follow instructions carefully! Some heaters are fully submersible, some or not. Wait at least 30 minutes before plugging your heater in! If you fail to do this you run the risk of causing the heater to shatter due to thermal inversion. Set the heater at a proper temperature. This may take some fiddling depending on your heater model.
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    Place the thermometer in/on the tank. Ideally most tropical freshwater fish enjoy a constant temperature in the 24 °C (75 °F) - 28ºC range. Research the species you wish to keep to learn about specific temperature requirements.
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    Place the aquarium hood and lighting on the tank. Note that most lighting will work for any species you keep, however additional research should be preformed if you wish to keep live plants. Live plants often require more than standard lighting. Some fish keepers find that attaching their light to a timer is beneficial.
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    Confirm that all cords have a drip-loop. A drip loop is a U-shape in the cord, so that if any water were to drip down the cord, it will fall to the floor instead of running into an electrical socket!
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    Test your water. Test for pH, carbonate hardness(KH), General Hardness(GH), Nitrites, Nitrates, and Ammonia. You should not have any Ammonia, Nitrite or Nitrate yet, unless your tap water contains these. Calcium carbonate (hardness) ties in to pH. If you have very soft water, the pH of your tank can become unstable. If your water is soft, add conditioning salt & KH Powder to your tank to prevent a pH crash. Most freshwater fish can live in a pH from 6.5 to 8.0. (7.0)is Neutral and preferred by most fish. Ask your aquarium to test your tap water for its pH level. If your pH ranges are above or below, ask the staff at your local aquarium for advice.
    • Remember that fish are very adaptable. They are more likely to get sick from a fluctuating pH than a stable but less than perfect one.
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    • Test your pH at least once per month and never let it drop below 6.0.
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    Sit back and relax. Grab a book or hop on the Internet and decide what kinds of fish you might like. You will need to wait at least 48 hours before adding your first fish. Adding too many fish too quickly is usually the worst of beginner's mistakes and usually leads to total tank failure.
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    Adding fish, and understanding your new tank. Adding fish is the most exciting part of setting up the tank! Unfortunately, it is often the worst mistake unless done properly. By following these steps, you will help to avoid the heartbreak of having all your fish die:
    • Let your tank run without anything in it for at least 48 hours. This helps the temperature stabilize. It allows you to make sure your water parameters are safe, and gives the dust and all parts of your tank to settle.
    • If you plan on keeping live plants, add them. They will help jump start the biological process needed to support live fish in your tank.
    • Take time to understand that your tank is not just a fancy cage for your fish. It is an entire ecosystem. Fish produce lots of ammonia- they produce it when they defecate, and they produce it as they breathe. That's what the filter is for, right? Well, yes and no. The filter only works properly when it is full of nitrifying bacteria. These are the good bacteria necessary to support your live fish. Without these bacteria, the ammonia that your fish make stays in the water and poisons your fish. Your brand new tank, being clean and newly set up, does not contain these good bacteria. If you add a group of fish without letting this bacteria grow in your tank, you are dooming your fish. This bacteria takes anywhere from 2-6 weeks to populate! So, what do you do? There are several methods of 'breaking in' or 'cycling' a tank... So, Cycle your tank.
    • If you know someone with a tank that has been set up for more than two months and with healthy fish, you can borrow some used filter media from them. Keep the media wet until you add them to your tank (gotta keep those good bacteria alive!). The good bacteria will have a jump start in populating your tank. If you don't know a friend with fish, you can purchase live bacteria in several forms from your local aquarium.
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    Add fish slowly. If possible, add no more than 1-2 smaller fish per 40 liters. For the first week, feed them very sparingly (a tiny amount) every other day. This is not cruel- remember if you overfeed at this point it may kill them. If you have your own test kit you can test your water daily, keeping a special eye on the Ammonia and Nitrite levels. If at any time the Ammonia or Nitrite spike to a dangerous level, perform a 20-30% water change. Never remove more than 30% at this stage (or you run the risk of killing your good bacteria off) and always replace with dechlorinated water. After a week it should be suitable for you to add a few more fish, and repeat the process. Barring any problems, you should have a stable tank within 4-6 weeks. After your tank is stable, you can feed on a regular schedule and can add fish as you desire. Remember: adding a large number of fish at a time sometimes causes the tank to become temporarily imbalanced, so use caution. Also remember that your tank can only support a limited number of fish per liter. This number depends on how large the fish is and its eating habits.


  • Before you buy fish - RESEARCH the species you want. Never buy on impulse, always research the fish at home so you don't buy an unsuitable animal for you.
  • Remember you are bringing living animals into your home and care and it is unfair to them to skimp on their needs. Be sure you have the finances and time to dedicate to an aquarium.
  • When you buy fish, you should provide them with a tank that will be big enough for the fish when they are adults
  • Bigger tanks are easier to keep stable than smaller tanks. You will find that keeping the water chemistry in a larger tank is much easier than in a smaller tank. Tanks smaller than 40 liters are often harder for the beginner to maintain. If you are a beginner, consider a tank of at least 20 liters unless you intend to keep a single siamese fighting fish .
  • Don't forget to continue to add good bacteria to your aquarium on a weekly basis.
  • Before putting ornaments like gravel and wood in the aquarium, make sure you rinse it thoroughly.
  • When adding fish such as Bettas (betta splendens) do not keep them in a community, as schooling fish nip their fins, and they fight with cichlids and other labyrinth fish.
  • Goldfish bowls can be considered cruel. Goldfish reach a minimum of 8" and can live 15 years or longer, and need a filtered tank. Goldfish are not a good beginner fish! For 1 goldfish, you need a 20 gallons tank, and you need to add 10 gallons on for each extra goldfish!
  • Bettas can be kept as a community fish but do your research on the proper tank mates.


  • Don't believe what the person selling you the fish tells you. In the US you are very lucky if you have a store near you that knows their stuff, as most don't. In the UK, the situation is slightly better but unless you are at a shop that is reputable among other aquarists then you should still be careful. Always do your own research!
  • Before purchasing your fish be sure to observe the tank that they are placed in for at least 15 minutes, looking for any signs of stress or disease. Putting a diseased fish into a new tank is asking for trouble!

Things You'll Need

  • Aquarium
  • Heater (or more than one, depending on tank size).
  • Filter (or more than one, also, depending on tank size).
  • Approximately 250g of substrate (gravel) per liter of water.
  • A cabinet
  • Tank thermometer
  • Test kit (Ammonia, pH, hardness, Nitrite, Nitrate)
  • Tank lid and light
  • Water dechlorinator/Conditioner
  • Patience

Article Info

Categories: Aquariums