How to Set up a Fish Tank (for Goldfish)

Co-authored by Doug Ludemann

Last Updated: October 28, 2024 Approved

You’ve probably seen pet goldfish kept in small glass bowls, but goldfish are actually much happier and healthier in bigger tanks with filters, gravel, and decorations. If you’re not sure how to start setting up your new fish friend’s tank, don’t worry. This article will walk you through everything you need to do step-by-step, from filling the tank to cycling the water to adding your goldfish.

Part 1

Part 1 of 3:

Choosing and Equipping a Goldfish Tank

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1
Consider the size of your fish tank. Goldfish require particularly roomy living arrangements in order to stay healthy. While they are pretty small fish, they need larger tanks than you might expect.
- You can do better than a bowl. Despite the beauty of a goldfish suspended in a sphere of glass, most fishbowls simply don’t provide enough room for their occupants.
- A single fancy goldfish can be kept in a 10 gallon (37.9 L) tank, but bigger goldfish like comets need a tank of around 50 gallons (189.3 L).
- If you like to add more goldfish to your tank, you’re going to need to increase the capacity of your fish tank by roughly 10 gallon (37.9 L) for each additional fish.
- A 20 gallon (75.7 L) is ideal for your first goldfish and can ultimately hold 2 fancy goldfish.
2
Decorate your fish tank. Most goldfish favor a palace or castle ambiance. Shoot for somewhere in between. Gravel is a must, and plants are recommended. In this range, follow these guidelines for your selection of décor, gravel, and plants:^{[1]
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- Choose a goldfish-appropriate gravel. Goldfish are scavengers, and they will pick up pieces of gravel and mess around with them just for fun. If the pieces of gravel are too small, your goldfish nay accidentally swallow them. To prevent that, use gravel that is made up of pieces that are too large for the fish to swallow.
- Objects such as rocks, caves, and plants will give your goldfish an opportunity to play around and investigate. Consider adding some to your tank.
- Don’t use wood. Though it looks spectacular, it will color your water and, depending on the type of wood, will dissolve.
- Be aware that some rocks and sea shells will affect the pH of the water. If you’re adding stuff you find on the beach willy-nilly, you need to check your tank's pH frequently.
- Only put certain plants in your goldfish tank. Goldfish, interestingly, are pretty aggressive with plants. Some plants are better able to defend themselves:
  - Try Vallisneria types, different Hygrophilas, Red Bacopa or even Ludwigia Arcuata.
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3
Use a filtration system. A filter is an absolutely necessary component of your fish tank. Filters operate according to flow rate, with certain filters designed for certain sized tanks, so make sure you get the right filter for a tank your size. There are two types to choose from.^{[2]
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- External filters rest on the exterior of your tank, while internal filters are submerged within the tank. Either type of filter can work for a goldfish tank.
- External filters are generally considered to be superior, as they have a greater capacity to store filtration materials and can accordingly clean water more thoroughly. .
- If you have a 20 gallon (75.7 L) tank, shoot for a filter rated for 40 gallons (151.4 L).
4
Add conditioned water. You can use tap water to fill your tank, but you need to add conditioner to make it safe for your goldfish. At minimum, you need a conditioner that neutralizes chlorine and chloramine.
- Aside from removing any harmful chemicals in tap water with conditioner, you’ll also need to make sure the water has the right pH level for gold fish, which is a slightly alkaline 7-7.5, ideally 7.2 pH. Use a pH test kit to periodically test your water, and adjust the pH if necessary.
- Take tank placement seriously. Do not place the tank near a window or any heating or cooling source. Do not allow sunlight to hit the tank directly. Also be sure the tank is set on something flat and extremely sturdy.^{[3]
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- You likely don’t need a heater. The fish tank’s water temperature should be between 60 °F (16 °C) and 72 °F (22 °C), so the ambient temperature of your living space should work.^{[4]
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Part 2

Part 2 of 3:

Cycling Your Fish Tank’s Water

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^{[5]
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Expert Source

Aaron Bernard
Fish & Aquarium Specialist

Expert Interview. 17 July 2020.} When you first set up your fish tank, you’re going to need to let the water sit for at least a few weeks before showing the place to any prospective goldfish occupants. This time is necessary to help build up beneficial bacteria, a process outlined in this section. Be patient during this process!
2
Change the tank’s water once a week. Let’s face it: goldfish poop a lot. And they hate swimming around in their own poop. You would too. Their poop will build up dramatically in your fish tank’s water (even with plenty of water changes), which will both enrage and sicken your goldfish. To curb this buildup, change 25-50% of the tank’s water once a week.
- When changing some of the tank’s water, rinse the filter and any tank décor with water your remove from the tank. Never use tap water. Healthy bacteria that you want to preserve live on and in these items.
- Only add clean water that you’ve treated with conditioner.
3
Cycle the fish tank’s water once a month. You also need to regularly cycle the fish tank, which means changing 100% of the tank’s water. The goal in cycling your fish tank is to allow it to rebuild colonies of helpful bacteria, which collect mostly on the filter and in the gravel. These bacteria help your water cycle nitrogen, which is necessary to keep your fish alive.^{[6]
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- Once your tank is setup and ready to go, with the filter running, add ammonia. Continue adding ammonia until enough bacteria have developed to eat both the ammonia and nitrites in your tank.
- There are various forms of ammonia, which is most readily available in bottled form. Follow the directions on the bottle.
- Determine your levels of ammonia, nitrites, and nitrates by using test kits designed for this purpose.
- Maintain the process until you get readings that indicate zero ammonia and zero nitrite. Once you also find a bit of nitrate in the water (which is produced by the bacteria), your tank has been successfully cycled.

Part 3

Part 3 of 3:

Introducing Goldfish to Their New Home

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1
Select your fish tank’s occupant. Look for a healthy, handsome fish. Don’t choose a fish from an aquarium in which there are also sickly or dead fish. You want a fish that looks like they’re aware of their surroundings, actively moves around, nibbles on stuff, and generally acts like a boss.
- Gaze into the fish’s eyes. Seriously. Goldfish eyes should be clear, not foggy.
- Check out the fish’s fins and body. You want erect, non-ragged fins on your fish. Saggy or messed up fins often indicate ill health. Similarly, don’t choose a fish with white spots, fuzzy patches, or red streaks.
- Once the match has been made, get your fish into a plastic bag filled with water from the tank from which it came. Place the plastic bag inside a paper bag so the journey to its new home will not traumatize it.
2
Show the fish its new home. But don’t hurry the process. Float the bag for fifteen minutes or so in your tank to let the fish slowly acclimate to any temperature difference. At about the five minute mark, allow some of the tanks water into the bag, but don’t let any of the bagged water into the tank.
- Do not pour the fish and the bagged water into your tank. Instead, gently scoop the fish out of the bag with a net and submerge the net in the tank slowly, letting the fish swim out of the net on its own.
- Turn off the lights and leave the room. Give your new goldfish some peace and quiet to encounter their new living space.
- Add a fish tank additive called stress coat to the water to minimize the chances of your fish becoming ill from the change in environment.
3
Feed your goldfish like it’s your only friend. There are a lot of different options. Get whichever you want; Preparation is more important. If the food is dry (most goldfish food is), soak it in water from the tank for a minute before feeding your fish. Un-soaked food can injure or sicken the fish when it expands in the stomach.
- Fish food should sink, or be suspended in the water. Food that floats risks giving the fish swim bladder issues.
- Feed your fish once a day, six days a week. On the seventh day, your gold fish needs to rest.
- Make sure not to feed to much; too much can lead to ammonia, while to less will starve your fish.

References

↑ http://www.about-goldfish.com/goldfish-aquarium-setup.html
↑ http://thegoldfishtank.com/goldfish-care/kit/do-goldfish-need-a-filter/
↑ http://www.goldfish-as-pets.com/tank_set-up.html
↑ http://www.goldfish-as-pets.com/tank_set-up.html
↑ Aaron Bernard. Fish & Aquarium Specialist. Expert Interview. 17 July 2020.
↑ http://thegoldfishtank.com/goldfish-care/tank/goldfish-tank-setup-water/
↑ Aaron Bernard. Fish & Aquarium Specialist. Expert Interview. 17 July 2020.

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Can I feed my goldfish fruits and vegetables?

Doug Ludemann
Professional Aquarist
Doug Ludemann is the owner and operator of Fish Geeks, LLC, an aquarium services company based in Minneapolis, Minnesota. Doug has worked in the aquarium and fish-care industry for over 20 years, including having worked as a professional aquarist for the Minnesota Zoo and Shedd Aquarium in Chicago. He received his Bachelor of Science in Ecology, Evolution, and Behavior from the University of Minnesota.

Doug Ludemann

Professional Aquarist

Expert Answer

I'd avoid it in general. Peas are okay, but I would limit the amount of veggies you give them. Too many fruits and vegetables are going to bog the fish up, which can lead to buoyancy problems, indigestion issues, and problems with bloating.

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Will my goldfish be okay with other fish?

Aaron Bernard
Fish & Aquarium Specialist
Aaron Bernard is an Aquarium Specialist and the Owner of Limited Edition Corals in Phoenix, Arizona. With over ten years of experience, Aaron specializes in aquarium maintenance, custom design, manufacture, installation, and moving. Aaron holds a BS in Biochemistry from Arizona State University, where he studied the effects of climate change on coral reefs and began to propagate his corals.

Aaron Bernard

Fish & Aquarium Specialist

Expert Answer

That depends! Goldfish tend to produce a lot of waste, which adds extra ammonia to the tank. Because of this, I would only recommend pairing goldfish with other hardy fish that can handle those ammonia levels.

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How do we identify a male and female fantail?

Community Answer

Look for tubercles. One of the main tell-tale signs that your goldfish is male, is the development of tubercles (small, white spots) on their gill-shields. Look for a thinner, more streamlined body shape. Look for a concave vent. Look for a midline ridge. Watch for chasing behavior.

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Goldfish produce a lot of waste, meaning other types of fish may not do well if paired in the same tank.^{[7]
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Expert Interview. 17 July 2020.}

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There a few ways to speed up the cycling process:
- During the cycling process, keep the water slightly warmer to increase the speed of bacteria growth.
- You can get a bottle of ready-to-go bacteria. If you go this route, still expect to add some ammonia and test until the tank is balanced.
- You can borrow bacteria from a friend who already has a well-established, recently cycled fish tank. Seed your own tank by taking some of their gravel or cutting off a piece of their filter’s sponge and adding it to your tank.
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Warnings

Not all types of goldfish are compatible. Check on compatibility before mixing different types of goldfish in your tank.

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Though you will likely need to set your fish tank near an outlet, don’t ever dangle electrical cords over your fish tank. Also be sure that no cord is pulling against the side of the tank or whatever your tank is resting upon.

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Don’t place anything sharp in your fish tank. Many types of goldfish have special eyes, which – oddly – actually makes it difficult for them to see. If they become frightened and move rapidly, they may injure themselves.

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