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How Many Goldfish in a 20 Gallon Tank?

How Many Goldfish in a 20 Gallon Tank?

A wide number of aquarium- enthusiasts have mentioned that Goldfish are truly amazing fish to pet. Ask anyone who pets a goldfish about how fascinating and appealing it is to watch them as they grow and are themselves.

However, even the oldest goldfish owners have questions regarding how many goldfish can live in a 20-gallon tank. 

Typically, 1 gallon of water is good enough for a one-inch fish. But, most goldfish is around 10 inches long. So, try to keep only two goldfish in a 20-gallon tank.

To answer your question in detail, this article is the perfect guide you can ask for. So, read on!

How Many Goldfish Can You Keep in a 20 Gallon Tank?

In the general run of things, it must be noted that 1 gallon of water is suitable for a fish equivalent to 1 inch. This goes to suggest that a tank as big as that of 20 gallons can become a house to 20 small goldfish.

However, an average goldfish can measure nearly 10 inches long. This tells us that not more than 2 fish should be kept in a 20-gallon tank!

Besides that, it is of utmost importance to keep the health and well-being of the goldfish in regular check. Also, ensure that there is just enough place for the fish to swim freely.

Of course, this number varies as per guidelines as well as the tank. If you are adding too many fish to the tank, there is a high chance you are creating stress among them. So, yes you should put a considerable number of fish in a 20-gallon tank.

goldfish feeding

How to Setup a 20 Gallon Tank for Goldfish?

The following are the required steps to perform to set up a 20-gallon tank for goldfish:

  1. The first step is to decide the place of the tank. It must be far from direct sunlight or air vents. 
  2. Thoroughly clean the aquarium and the related materials with water. Make sure to remove all the dirt stuck there.
  3. Then, carefully place some crushed rocks right at the tank bottom. Make sure they are cleaned thoroughly and free from any debris. 
  4. According to your taste, start decorating your aquarium with plants and other decorations to make it look lively. For instance, you can add a shipwreck toy or put a tropical forest decoration. 
  5. Start filling the tank slowly with water ranging between room temperature. Do not pour the water directly on decorations or even a plant as it may disturb the substrate. After filling the tank with water, add a good conditioner amount suitable for water.
  6. Next, bring the air filters and water heaters into the picture. Try to adjust your heater to approximately 70 degrees Fahrenheit. Never activate or plug in the same until both the instruments have been completely covered with water. 
  7. Check the temperature of the water and its parameters before putting it in the goldfish. This is a crucial step for their safety. 
  8. It is highly suggested that you observe the goldfish for a couple of days. Give them the time they require to come to terms with their new environment. Slowly, they will start to acknowledge their beautiful surroundings

Goldfish Tank

Can I Keep a Fancy Goldfish in a 20-Gallon Tank?

Yes, you can keep a fancy goldfish in a 20-gallon tank. All you need to do is observe them for a day or two to see if it is responding well. However, finding out the proper aquarium size can be seen as a debatable point of discussion.

On a usual basis, fish experts suggest 20 gallons of water should be good per goldfish. A new 10 gallons volume of water must be added if a new goldfish enters the aquarium.

Regardless of whether the goldfish is a fancy one or not, putting a single goldfish in a tank full of 20 gallons of water, it will ultimately need more space after some time. Also, there will be no other option left but to change the water now and then because of keeping the tank clean.

On the other hand, if you were to add an approximate number of four or five goldfish in a 60 or 70-gallon aquarium, the tank will ask for little maintenance at the maximum. The cleaning schedule becomes manageable in the long run.


How Long Do Goldfish Live in a 20-Gallon Tank?

It is a mistaken belief that goldfish do not live long. Some individuals believe it to be true while others don’t fall for the misconception.

It is a known fact that these fish are part of the Carp family tribe. This means that their lifespan goes as long as 20 years. They can easily adapt to living in the wild as well as in a captured area such as a tank.

A domesticated breed like that of a goldfish coming from the wild Carp kinship can live longer when it is kept in an exterior fishpond structure that has a close association with its natural environment.

If you plan on petting this variant, it is important for their tank to at least hold a capacity of 50 gallons. The life expectancy they lead is influenced by the amount of care they are under and their breed as well. 

So, without any doubt, fancy goldfish need a greater level of care as compared to other breeds. Other fancy goldfish include Ranchu and the bubble eye which has a lifespan of only half a decade.

Telescopes, Fringetails, and Fantails are fish that can live up to a period of 12 to 14 years, depending on how they chose to surround themselves. Such breeds can attract issues related to vision and motion coordination.

Also check: How Many Goldfish Can You Keep in a 10-Gallon Tank?

How to Maintain a Small Tank?

A healthy atmosphere is what every goldfish would want. No wonder, maintaining a small tank requires a lot of time and energy. 

Given below are some helpful points on how to maintain a small tank for your goldfish.

1. Perform Water Checks Regularly

The first and the most important tip would be monitoring water changes once in a while. There are a variety of products that can help keep the water parameter in check but they contain chemicals in plenty.

It is best to replace the dirty water with clean and fresh water as it is always a better option. So, avoid using odd substances.

Another way to maintain a small fish tank is through regular water changes. Doing this will not only prove healthy to the fish but also the tank.

However, by any chance, if you are finding it difficult to maintain the water parameter, take action immediately. You do not want the water to get polluted and your fish to get harmed.

2. Clean Tank Glass

If a little green spread appears on your tank glass, there is not much to worry about! But if there is plenty of the same, there is a distressing factor right there. Not only is it harmful to the fish but it lays a bad and murky impression on the tank.

Oxygen found in the water also diminishes with time. Now, with oxygen decreasing, it can lead to the death of fish and marine plants.

3. Avoid Over-feeding the Fish

A basic rule that goes along with the maintenance of a small tank is to not overfeed the fish. 

When you overfeed your fish, it may result in several problems including an increase in the quantity of rubbish and debris collected in the aquarium.

Fish can survive even with a little pinch of food. Stuffing them with food contributes to the growth of algae. This action leads to the degradation of the quality of water and oxygen. 

Thus, avoid overfeeding. Instead, try to have a constant feeding routine, providing them with just enough food to keep them healthy.

4. Take out the Gravel

Have you ever heard of the method by which water is siphoned? Well, these are long tubes with a vacuum attached to it at its end. You need to set the unattached tube end in the tank water.

Slowly, apply a little pressure on the vacuum against the other end. With the task executed, you will notice waste collected in the gravel. 

Repeat the process till you are satisfied with the fish tank. Remember to wash your hands with a bar of antibacterial soap before putting your hands over the gravel.

Also Check: How Often Should You Feed Goldfish?

5. Remove Unwanted Decorations

Getting rid of unwanted decorations in the fish tank is yet another tip for maintaining it. It is not necessary to remove them completely; replacing them with small objects can do the job. 

You can take the help of an algae pad or a new toothbrush for cleaning purposes. Under no circumstances should you make use of washing-up liquid or any kind of chemical soaps to clean the decorative articles. 

There are high chances that the fish may die due to the deadly chemicals and toxins in the soap.

Even the growth of algae greatly contributes to meeting this consequence. Thus, it is wise to remove unwanted decorative materials!