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The Most Common Freshwater Aquarium Fish: Which One Is It? 

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Freshwater fish are a great option for those looking for a beautiful tank without too much hassle. They are known to be tolerant and most do great in a community tank. However, some are more popular than others.

The goldfish seems to be the most popular freshwater fish. They are often found in pet stores with a variety of colors, or even at the local fair. They are very resilient fish and can do well under numerous circumstances. However, most are not taken care of properly and are in bad condition.

Goldfish are very common, but there are several runner-ups that are best for a first-time aquarium owner. We will go over what a goldfish actually needs to thrive and other fish that may be a better fit.

The Goldfish 

Goldfish are the most common freshwater aquarium fish. They are the typical first pet for kids since they are hardy.

They are more resilient than other freshwater fish and are easier to care for. They are also a cheaper option when purchasing fish. 

Goldfish in aquarium with green plants

Despite what some people think, goldfish can grow fairly large. They also grow to the size of their environment and are not meant to stay small.

Goldfish are hardy fish that are resilient to water changes and more. They can actually live for up to 15 years if taken care of properly. 

Goldfish can also come in a variety of different colors, rarity, and shapes. The common goldfish, which is the kind you see in most homes, have a slim orange body with a single tail and are the most basic, inexpensive, and easy to care for.

There are “fancier” goldfish that come in different shapes and colors than the common goldfish, such as a Ryukin Goldfish.

A ryukin has an egg-shaped body and a high shoulder bump. 

Water Parameters 

Goldfish need to be kept in the following water parameters in order to thrive:

  • Temperatures: between 65°F to 72°F 
  • pH Level: 7.0
  • Water Hardness: 50- 120 ppm

Keep in mind that with a fancier goldfish, you will need to be more cautious with the water parameters listed above. Research in your specific breed is key.

Tank Size

While goldfish are commonly found in fishbowls, they should not be in such small spaces.

They need to be in a fish tank of at least 20 to 30 gallons in volume. Again, they grow quite large, and being in a small tank will hinder their growth.

On top of this tank size requirement, there should also be 10 gallons of extra space per additional goldfish that you add to the tank.

With that being said, goldfish can either be alone in the fish tank, or they can have tank mates. 


Guppies are another great starter fish. They can adapt to a variety of different water conditions and are also very easy to care for.

They come in a variety of colors (the males are more colorful) and are very playful fish. 

Since they have such beautiful colors and get along with other species of fish, they are very popular starter fish. They are also on the smaller end of the spectrum and you can fit more of them in a tank.

If you do not plan to breed your guppies, it is best to keep only males or females in the tank.

This is because they breed very quickly and you can have an overpopulated tank very quickly. Again, if you want to color, you will want males. 

Water Parameters

  • Temperatures: Between 72°F to 84°F
  • pH Levels: 6.8- 7.8
  • Water Hardness: 8- 12 gH

Tank Size

A 10-gallon tank is a good size for guppies, following the general rule of one gallon per fish. For example, if you have a 10-gallon tank, you can have up to 10 guppies.

However, keep in mind that you will want a larger tank if it has larger decorations. 

Guppies are a very sociable breed and should be kept in groups of about three at the very least. Again, be careful not to mix males and females unless you are planning to breed the fish.


Mollies, like the guppy, are a smaller breed of fish that adapt to different water conditions.  They are easy to care for, making them another popular choice for beginners. 

Like the guppies they do breed quite a bit so it may be best to keep only males or females depending on your experience and if you desire to breed.  Mollies also come in a variety of colors.

Water Parameters

  • Temperatures: between 72- 78
  • pH Level: 7.0- 7.8
  • Water Hardness: 15-30 gH

Tank Size

It is best to house your mollies in a tank of at least 20 gallons. A 20-gallon tank is acceptable if you choose only to have a few Mollies in your tank. This is because they can grow to about 3-4 inches in size.

However, the larger the better so they have enough room to swim; especially if you have other breeds in the tank.

They do get along well with different fish such as guppies, platies, and bottom-dwellers. This makes them perfect for a freshwater community tank.


Swordtails are another common breed of fish for beginners. They are a bit larger than guppies and mollies but are docile. They come in a variety of colors as well and can give your tank a boost of colors. 

Water Parameters

  • Temperatures: between 65°F to 82°F
  • pH Levels: 7.0 to 8.4
  • Water Hardness: 12 to 35 GH

Tank Size

Swordtails should be kept in a tank that holds at least 10 gallons. However, a larger tank is recommended, especially if you have a few of them. They are very active fish and love the extra space. 

If you have a community tank, you will want at least 20 gallons. Keep in mind, swordtails spawn at an alarming rate and you will not want to mix males and females unless you plan on breeding them.

With this in mind, it is important to note that swordtails do very well in a mix of other species of fish, but they are livebearers. If they spawn, you will have fry in the tank that could be eaten quickly by other species. 

Betta Fish 

The Betta Fish, or Siamese Fighting Fish, is a common choice for those who do not want the hassle of a larger tank, or those who don’t want to take care of multiple fish.

They come in beautiful colors and can be kept in a smaller tank. 

Water Parameters

  • Temperatures: between 75°-81°F
  • pH Levels: 6.5-7.5
  • Water Hardness: 3-4 GH

Tank Size

While it is common to see betta fish at the local pet store in small plastic containers, this is not the best environment for them.

Betta fish do great in a tank of at least 5 gallons. This ensures that they have room to swim and explore their surroundings. 

Despite what is advertised, betta fish actually love to explore their environment.

With this being said, they are very territorial. This means that a betta fish should always be alone in their tank. If you add another fish to the fix, they will fight. 

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