First Goldfish Tank Guide

Goldfish can make excellent pets! 

But, if your new fishy friends are going to thrive, you’ll need to know a few basic things about how to set up your goldfish tank properly.

Read this guide to find out everything you need to know about setting up a new goldfish tank.

What Size Goldfish Tank Should You Have?

To know what size goldfish tank you need, the first thing you need to decide is how many goldfish you want to keep as pets.

Goldfish do best when kept in pairs or small groups of the same type. You shouldn’t keep one goldfish on its own. A solitary goldfish will quickly become lonely and stressed, which can lead to health problems.

So, you want at least two fish.

The goldfish you buy in pet stores are typically just a couple of inches long. That’s because these little cuties are baby fish; just a couple of months old.

But don’t be fooled! Did you know that an adult Fancy Goldfish can grow to measure up to 8 inches long? Slim-bodied species of goldfish, such as Comets, can get even bigger, often reaching over a foot in length! Now, that’s much too big for most goldfish tanks.

What type of goldfish to keep?

Since Comets and other similar types of goldfish are best-suited to life in a fish pond where they have plenty of space to swim, you want to focus on having Fancy Goldfish as pets. We recommend choosing ordinary Fantails, rather than some of the more unusual varieties. Species such as Telescope or Bubble Eye Goldfish can be more challenging to care for, so they are best avoided until you have more experience.

What size tank do I need for my first goldfish?

The more goldfish you keep, the more space they need. 

At first, while the fish are just a few inches long, you can have a tank of 20 gallons per fish. So, fishbowls, 5-gallon, and 10-gallon tanks are simply too small and are unsuitable homes for goldfish.

But why do you need such a large tank for a few tiny fish?

Well, goldfish are very messy fish! Goldfish eat a lot and generate masses of waste. Fish waste creates a chemical called ammonia at the beginning of the nitrogen cycle. Ammonia is highly dangerous to your goldfish, and if too much ammonia builds up in the water, it can stress or even kill your pets. 

So, you need a large tank with plenty of water to dilute the ammonia.

As your goldfish grow, you must upgrade your tank to a 50, 75, or even 100-gallon tank for just two large goldfish! 

Tank Shape

The best shape of tank to choose is a rectangular one.

  • A rectangular tank is best for gaseous exchange, so your fish get all the oxygen they need to survive.
  • Rectangular tanks provide plenty of swimming space for your goldfish.
  • A long, shallow tank is best for round-bodied fancy goldfish. These fish are not good swimmers, and they might struggle to reach the water surface to feed in a tall, deep tank.
  • The tank also needs to have a tightly fitting lid or a cover slide. 

Although Fancy goldfish are not known as jumpers, accidents do happen when the fish are young, and you don’t want your pets to finish up on the living room carpet!

A lid also prevents the water from evaporating and keeps dust and other debris from falling into the tank and polluting the water.

Goldfish Tank Equipment

As well as a goldfish tank of the correct size, you’ll also need to buy some other essential pieces of equipment.

Filtration System

As we mentioned earlier, goldfish are very dirty fish that produce lots of waste. You’ll need to carry out partial water changes every week to remove that waste and keep the water safe for your fish. 

But you’ll also need an efficient filter system to help process the fish waste and keep the water clean and safe for your pets.

The filter system must be the correct size for the tank you have, ideally circulating the water throughout the tank and over the filter media at least four times every hour throughout the day and night.


Fish don’t really need much light to be happy. If you think about it, a goldfish living in a pond only has natural light and does well enough.

However, goldfish in a tank do need a clear day/night cycle. In nature, fish have the sunrise to tell them when it’s time to get active and feed. At night, the sun sets, so the fish know that it’s time to rest and sleep. If captive fish in a tank don’t have that natural light cycle, they can become stressed and sick.

Living plants are great for fish tanks! Plants produce oxygen and remove carbon dioxide from the water, keeping the environment healthy for the fish. In addition, nitrates and other potentially harmful waste products in the water are absorbed by plants for use as fertiliser. 

Plants need between eight and ten hours of light every day for photosynthesis. Without enough light, the plants will eventually die. So, for the benefit of both your goldfish and your plants, you’ll need a lighting unit for your fish tank.

Light Timers

Some lighting units have an auto-timer feature that you can set to switch the lights on and off at preset times. That’s great, as it means you don’t need to be around to manually activate the lights.


Goldfish need lots of dissolved oxygen in their water to stay healthy and thriving, and a bubbler provides extra oxygen for the fish. 

Bubblers come in different shapes and designs. You can choose from a shimmering curtain of bubbles at the back of your fish tank, a single column of bubbles in one corner of the tank, or even a funny scuba diver ornament bubbler!

Aquarium Thermometer

Goldfish are coldwater fishes that like a cool water temperature. Fancy goldfish prefer the water temperature to be 68° to 74°F, while comets and shubunkins should be kept between 60° and 70°F.

Although you don’t need a heater for a goldfish tank, we recommend that you use an aquarium thermometer to keep an eye on the water temperature to make sure it doesn’t get too warm for the fish. 

You can avoid water temperature problems by keeping your tank away from direct heat sources, such as radiators, fires, and direct sunlight.

Fish Tank Kits

Now, it can work out quite expensive to buy all those different pieces of equipment. However, you can choose to buy a complete fish tank kit instead of buying each item of kit separately, and that usually works out much cheaper.

Kits usually contain the fish tank and lid, a lighting unit, and a filter system.

As an added bonus, you often get some substrate, fish food, a few decorations, and some replacement filter media included with the kit, saving you even more cash to spend on your goldfish!

Simple Goldfish Tank Decoration

Goldfish don’t really mind what their tank looks like, so the style of decoration that you choose for your goldfish tank is really up to your personal taste.

  • You’ll need some kind of substrate to cover the bottom of your tank. Smooth gravel works well, and you can choose from natural or colored substrate.
  • Smooth stones, glass pebbles, and rocks look good and add interest to the tank.
  • Pieces of smooth driftwood and bogwood look great.
  • Resin ornaments can add interest to the setup, and there are plenty to choose from.

When choosing decorations for your goldfish tank, make sure that the items you choose don’t have any sharp or rough edges that could harm your fish.

Fish Tank Plants

Living plants make an excellent addition to any fish tank. Plants produce essential oxygen that your fish need and take up carbon dioxide. 

Living aquatic plants also use nitrates that could harm your fish as fertilisers, helping to keep the water clean and easing the burden on your filter system.

Choose robust plant species that can withstand the goldfishes’ habit of digging around in the substrate and won’t mind being nibbled on occasionally by the fish. 

Good plants to use include Marimo Moss Balls, Java Fern, and Anubias, all of which you can buy relatively cheaply in your local pet store.

Goldfish Food

Goldfish are omnivores. That means the fish enjoy a diet consisting of plant matter and some meaty protein. 

Your fishes’ staple diet should include goldfish flakes or pellets. That food is specially formulated for round-bodied fancy goldfish, helping to prevent common digestive problems, such as constipation and bloat.

Meaty foods also aid digestion and keep things moving through the fish, so you should also include a portion of meaty protein in your fishes’ daily diet. 

The best choice for tank-kept goldfish are frozen foods, such as bloodworms and daphnia. Frozen foods come in convenient packets of cubes that you can keep in your home freezer. Simply thaw a cube in some tank water, and then offer it to your goldfish.

Goldfish graze on algae throughout the day, so it’s fine to leave a few inconspicuous patches of the green stuff for your pets to snack on between feeds. 

You can also give your fish some blanched veggies, such as zucchini, cucumber, lettuce, and spinach once a week or so as a treat.

Can I feed my goldfish live food?

Goldfish living in a garden pond will enjoy the addition of live foods in their diet. 

Insect larvae, waterbound insects and tiny worms are also available for the fish to eat, especially during spring and summer.

Although you can buy live food from pet stores, it often contains parasites and bacteria that could make your goldfish sick. For the same reason, you should never take live foods from the wild environment!

Instead, we recommend that you use frozen meaty foods to provide your pets with the nutrition and protein they need.

How much should I feed my goldfish?

Goldfish are notoriously greedy fish that will eat as much as you’re prepared to give them! However, overfeeding can make your fish sick, and any food that’s uneaten will pollute the water in your fish tank.

Ideally, you should feed your fish only what they will clear up in a couple of minutes.

How often should I feed my fish?

It’s better to feed your fish two or even three small meals every day, rather than one big one.

Feed your fish once in the morning when your aquarium light comes on and then offer another feed in the afternoon, when you get home from school or work.

I feed my fish a portion of goldfish pellets in the morning and some frozen food or veggies in the afternoon, which works very well.

Tips For Goldfish Beginners

Here are a few helpful tips and hints for newbies to the goldfish keeping hobby:

  • Buy the correct size fish tank for your fish.
  • Add fresh plants to your fish tank.
  • Keep the tank clean and healthy by installing a filter system and maintaining it correctly.
  • Carry out 30% partial water changes every week.
  • Install a lighting system in the tank so that your fish have a clear day/night routine.
  • Feed your fish a varied, high-quality diet that includes fresh veggies and frozen meaty protein.
  • Don’t overfeed your fish!
  • Check your goldfish every day to ensure that they are active and are eating well.
  • Check your fish every day for signs of disease, such as swellings, red patches on the skin, ripped or torn fins, swimming on one side, not eating and lack of activity.

In Summary

Did you enjoy our guide to keeping your first goldfish? If you loved the article, please share it!

Goldfish are relatively easy to keep, provided that you have a large tank with an efficient filter system to keep the environment clean and healthy. 

Feed your fish twice a day on a varied diet of goldfish pellets or flakes, frozen meaty protein, and fresh veggies. Watch out for signs of disease, and treat the problem with an appropriate medicine that you’ll get from good pet shops.

How many goldfish do you keep? What variety of goldfish do you have? Tell us about your pets in the comments box below.

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