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How to Buy Freshwater Aquarium Fish (With Community Tank Ideas)

Having worked with fish most of my life, I have a strong desire to help others to be successful in the hobby.

Three Spot Gourami

Three Spot Gourami

Buying Fish for Aquarium

Spotting that perfect fish and bringing it home without any preparation makes it likely that the fish won't live through the experience. It is important that you only purchase one or two fish at first, depending on the size, before adding more fish. This will help the nitrogen cycle start to develop in your tank.

After a couple of weeks, you can then add another fish and wait for the aquarium to adjust before adding more fish. Never add more than a couple of fish at a time. This can disrupt the nitrogen cycle, creating a deadly environment for your fish.

Guideline: 1 Inch of Fish per 1 Gallon of Water

As a general rule, you should be able to keep 1 inch of fish for every gallon of water if it is properly filtered and aerated. Don't forget to take into consideration the ultimate size your fish will grow to as it matures.

Your fish tank should already have been set up for at least 24 hours (much longer for saltwater) and should have been properly prepared for the type of fish you intend to purchase.

Supply List

Great starter kits can be found at your local pet supply store. These kits are usually much less expensive than buying the individual parts separately.

At a minimum, you will need the following equipment before purchasing your fish:

  • Tank
  • Hood and Light
  • Heater
  • Filter
  • Gravel
  • Fish Food
  • Decorations and Plants
  • Net
Example of a basic aquarium starter kit

Example of a basic aquarium starter kit

Tips on Selecting Fish

Consider the health of the fish you want to buy, as well as whether they get along with all of the species you want in your tank.

Buy Good, Healthy Fish

Buy only good, strong, healthy fish for your aquarium. Introducing weak or injured fish to your tank can also introduce deadly diseases killing everything in the tank.

Watch for any signs of disease in the tank where you purchase your fish. Any signs of dead fish, white spots (ick), torn fins, or patches that look like cotton are all signs of disease that you could be taking home to your own tank.

Check the Compatibility of Aquarium Fish

To ensure the health and well-being of your freshwater tropical fish, it is important that you select species that are compatible with each other. Many varieties such as the African Cichlid are known for their aggressiveness and will not get along with other types of fish.

How to Create a Community Tank

One of the best ways to ensure the compatibility of the fish in your aquarium is to create a community tank. Community tanks are collections of fish that are known to get along and have similar environmental and dietary needs.

The following are some examples of different types of community tanks you may wish to try.

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One of the easiest community fish tanks you can have is a goldfish community tank. Goldfish can grow to considerable sizes so be sure to take this into consideration when creating a goldfish community tank.

Goldfish should only be kept with other Goldfish or Koi. While you may be able to find fish that can handle the cold water environment that Goldfish enjoy, Goldfish have different dietary needs and rapidly outgrow other tank mates.


Guppies come in a wide variety of colors and have been bred to produce several different types of exotic fin shapes. Breeding guppies are very easy producing a brood every four to six weeks. Each brood may have several dozen baby fish or fry. Guppies enjoy eating decaying pieces of aquatic plants so live plants provide an important part of the guppy diet.


A livebearer aquarium can be one of the easiest tanks to set up. Livebearers are usually quite hardy and come in a wide variety of colors.

Your livebearer fish are bred very easily. If you do choose to try to breed your livebearer fish be sure to provide plenty of hiding places for the fry so they don't get eaten and move them to a different tank as soon a possible.

Male (top) and female (bottom) Mollies

Male (top) and female (bottom) Mollies


Mollies are very easy to take care of and will do well in a community aquarium with Livebearer fish. Although mollies can live their entire lives with other Livebearer fish, they do best if kept in brackish water.

The additional salt in brackish water helps them maintain a healthier slime coating and lowers stress levels.


Platies are very easy to take care of and comes in a wide variety of colors. There are even been some unique shaped Platies. Platies, like Molies and Guppies, are very easy to breed.

Under certain circumstances, female Swordtail can change into a fully functioning male.

Under certain circumstances, female Swordtail can change into a fully functioning male.


Swordtails can provide additional interest for your aquarium. Most Swordtails are quite peaceful however they may be aggressive at times. Be sure to have a good lid on your aquarium to prevent them from jumping out.

Male Swordtails have a sword and the females generally don't. In an aquarium of only female Swordtails, a female Swordtail can actually turn into a fully functional male. Often older female Swordtails will grow a gonopodium (male productive organ) and a sword on their tail.

Bleeding Heart Tetra

Bleeding Heart Tetra

Danios and Tetras

Danios and Tetras are schooling fish and should have at least three of each species in the aquarium. Both Danios and Tetras are very easy to take care of and usually provide lots of activity for your aquarium.

If given the proper environmental conditions and diet, some Tetras and Danios are fairly easy to breed. Danios and Tetras are egg layers.


These cute little guys in the image above can grow to huge sizes. Be prepared to have a huge tank for these hungry Oscars.

African Cichlids

If you don't want the cost of a saltwater tank but like the bright colors of saltwater fish, African Cichlids may be the perfect choice for you.

These fish are known for their aggressiveness and won't get along with any other types of fish. They are also known to destroy just about anything in their tank so live plants are not a good choice in African Cichlid tanks.

Jack Dempseys

Named after the 1920s heavy-weight boxer for its love of beating up other tank mates, this South American Cichlid is quite aggressive and is best kept with fish that are similar in size and temperament.

Jack Dempseys are beautifully colored and can grow to over 12 inches long, so they require lots of swimming room. Jack Dempseys become much more aggressive if kept in cramped quarters. Provide them with lots of hiding places and don't be surprised if it rearranges the tank décor from time to time.

If you happen to get a pair, you have a good chance of breading the Jack Dempsey if they are given the proper environmental and dietary considerations.

The Boesemani Rainbow is an active schooling fish.

The Boesemani Rainbow is an active schooling fish.

Mixed Fish Variety Community Tanks

To have a more interesting aquarium, you may wish to mix different species of fish together. Special care must be taken to make sure that all of your fish will get along and that they all have similar dietary and environmental needs.

You should also keep in mind the zone that the fish usually inhabits. Does it like to swim at the top, bottom or in the middle of the aquarium? An ideal aquarium will have all three zones occupied.

Here is an example of some of the fish that you could add to the same tank to get a nice community aquarium if desired:

  • Most Barbs
  • Cory Cat
  • Most Danios
  • Loaches
  • Sharks
  • Swordtails
  • Tetras
  • Rainbow Fish
  • Plecostomus
  • Platies
  • Mollies
  • Most Gouramis

Remember: Learn About Your Fish Before You Buy

In any case, learn about the fish you intend to buy before you purchase it. Fish like the Kissing Gourami above look friendly enough in the pet shop but can raise havoc in your tank if placed with the wrong tank mates.

Other Fish and Creatures to Add to Your Aquarium

You may be interested in adding some bottom feeders or other aquatic creatures to your tank, like shrimp. There are special considerations to keep in mind for these fish as well.

Fish That Provide Special Services

Some fish help to keep your aquarium free from algae and excess food such as the Plecostomus and Chinese Algae Eater.

  • Chinese Algae Eater: Use caution when purchasing a Chinese Algae Eater, aka Sucker Fish, as they can get quite aggressive as they get older. The name Chinese Algae Eater is kind of a misnomer because they don't do that much to clean algae from the tank. They are best for cleaning excess food from the bottom of the tank.
  • Plecostomus: These fish are great at getting rid of algae; however, they grow rapidly and can soon become unmanageable in a small aquarium.
  • Cory Cat: This fish does a great job of cleaning the bottom of the tank and will get along with most peaceful fish. The Cory Cat makes a great addition to a peaceful community aquarium.