Setting up a Freshwater Aquarium

Updated Sep. 8, 2023
Freshwater aquarium

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Freshwater aquariums can be a great way to start keeping fish. They can add activity and beauty to any room in your house, and these vibrant aquascapes promote a calming presence. Aquariums are also a great way to engage children and educate them about fish and chemistry.

Choosing an Aquarium

There are many considerations to factor when determining what type of aquarium you want to establish. These include the size of space available for the aquarium, the fish species you’re interested in housing, including how long they live and grow in size. Most fish do well in a horizontally laid out aquarium. However, successfully aquascaping any tank can provide small microhabitats (smaller habitats within a larger habitat) for the right species to thrive.

What Do You Need for a Freshwater Aquarium?

Choose an aquarium that is the correct size for the species you intend to keep. Other necessary materials may include:

Where Should You Place Your Aquarium?

Selecting an aquarium’s location is key for multiple reasons. Make sure that the aquarium is not in direct sunlight, since this can promote algae growth making it harder to keep the aquarium aesthetically pleasing. Additionally, too much sunlight can stress out some fish species.

Avoid placing any aquarium near windows, outside doors, heat vents, and air conditioners as these can impact the water temperature. Rapid changes in water temperature can be stressful and even life threatening to some fish.

Water for Freshwater Aquariums

Water should be prepared before adding into any aquarium. Providing a water conditioner will help to neutralize any elements that are toxic to fish. Do not use tap water for a home aquarium without conditioning the water. Municipalities add chemicals to tap water such as low levels of chlorine to help maintain drinking water standards, but these levels are toxic to fish.

Water temperature control can easily be provided by a heater and a thermometer in the aquarium. Some temperature controllers can be used as backup to ensure a heater doesn’t fail and decrease the temperature of a tank too much.

Maintaining oxygen saturation in the water can be provided by an aerator and specially designed filters. Always have a freshwater water test kit available to test your water at home.

Decorating Your Freshwater Aquarium

Rock/pebbles or gravel are frequently used as substrate in freshwater aquariums. Rocks and wood pieces can be used to create small hiding spaces within an aquarium. Caves and hiding spots give fish the opportunity to demonstrate natural behaviors.

Fake plants are often used to help aquascape enclosures, these are easily removable, easily cleanable, and do not carry and bugs into the aquarium. Live plants can provide a beautiful aquascape–however additional equipment is needed to ensure the plants thrive.

Additionally, other substrates need to be used to establish the plant roots. Live plants do provide a beautiful display but have their challenges.

How To Set Up Your Freshwater Aquarium

Choose a Location

Avoid a location where rapid temperature changes occur. Also, water is quite heavy and a single gallon weighs about eight pounds. Ensure that you have enough support to withstand this amount of weight wherever you place your aquarium.

It’s also important to ensure the location you choose has adequate power nearby so the equipment powering the aquarium can run uninterrupted.

Preparing Your Aquarium

  1. Rinse out your aquarium and clean it of any dust or debris. Inspect the aquarium for cracks in the glass.

  2. Place the aquarium stand in the desired location and ensure it is level.

  3. Ensure there is room between the wall and the aquarium to fit life support, such as filters and cords. This can also make maintenance easier.

  4. Add any background to your aquarium before filling it with water.

  5. Fill the tank one third of the way to evaluate for any leaks. You will notice water on the bottom edge of the aquarium accumulating. If you notice any leaks then do not use this tank to establish your aquarium.

Building Your Aquarium

  1. Install your filter according to the instruction provided by the filter manufacturer. Do not turn on your filter until water is in the aquarium.

  2. Add in substrate. Rinse any new substrate before placing it in the aquarium. You can do this with a colander.

  3. Add in all the decorations and establish your aquascape once the substrate is placed.

  4. Condition the water before adding it to the aquarium. Add the appropriate amount of water conditioner to the aquarium per the manufacturer instructions.

  5. Install the air stone and air pump. This will add aeration to the water.

  6. Fill up the tank with the conditioned water.

  7. Place the heater into the tank. Install the heater based on manufacturer instructions.

    • Some heaters are completely submersible while others hang off the edge of the aquarium. Follow the instructions of the heater to turn it on and allow some time to let the water to get to the correct temperature. The best temperature range will depend on the species that you place in your aquarium, ranging from 72­­–82 F. Additionally, pick the correct heater for the size of your aquarium.

  8. Install a thermometer based on manufacturer instructions. This should be placed away from the heater and in an easy-to-check location.

  9. Install the overhead light.

  10. Plug in all equipment including lights, filter, air pump and heater. Ensure the cords run from the tank and touch the ground before looping up to the plug—this prevents water from running down the cord and into an electrical socket.

Establishing Your Biofilter (Stabilizing Period)

Test water daily to determine the concentrations of ammonia, nitrate, and nitrite. Ammonia and nitrite can be toxic to fish. Adding in nitrifying bacteria early will help establish the biological filter and will also speed up the cycling process.

Freshwater Aquarium FAQs

How long do you have to wait to put fish in a new tank?

Most importantly, ensure the beneficial bacteria has had enough time to stabilize the tank. These will help breakdown the toxic waste of the fish that is produced in the system. Fish can be introduced into an aquarium once all the water quality parameters have stabilized, including temperature, pH, ammonia, nitrate, and nitrite. Once you have the parameters stabilized and there is no ammonia or nitrite in the system, then you can safely add fish to the aquarium.

How do I know when my aquarium is ready for fish?

Weekly water testing can help you determine when it is time to add fish to your aquarium. When a tank has a stabilized pH, no ammonia or nitrite present in the water, this is an indication of a healthy biofilter.

How long does it take to establish a freshwater aquarium?

It can take anywhere from 1–2 weeks to establish a freshwater aquarium. Some companies now produce bacteria to add to the tank to help speed up the cycle time and expedite your ability to add fish to the aquarium safely.

Can you set up a fish tank and put fish in it the same day?

This is not recommended. Tanks that are set up the same day have not been able to cycle long enough and have a biological filter develop. This increases the risk of fish dying from either ammonia toxicity or nitrite toxicity.

What happens if you put fish in a new tank too soon?

If fish are added to a tank too early then tanks can develop new tank syndrome and fish can die from ammonia toxicity. Additionally, if the biological filter is not established completely, nitrite toxicity can develop. This is known as brown blood disease. Fish are very sensitive to nitrite. Allowing a fish tank to cycle appropriately allows the biological filter to convert ammonia to nitrite, then to harmless nitrate.

Featured Image:

Sean Perry, DVM


Sean Perry, DVM


Dr. Sean Perry completed his undergraduate degree at the University of California, Santa Cruz, earning a Bachelor of Science in...

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