If you want to know how many fish you can keep in a 40-gallon tank, then you’ve found the right article! In this article, not only will you learn how many you can keep, but you’ll also learn the best types of fish you can keep as well as things to be aware of when you’re stocking your tank!
So keep reading to find out everything you need to know!
How Many Fish In A 40 Gallon Tank?
As a rule of thumb, you should keep 1 inch of fish per gallon of water. So if you wanted to keep fish that grew to two inches in size, then you’d be able to keep roughly 20 before the tank was overstocked.
However, other considerations, such as the temperament of the fish, would also need to be taken into consideration!
What Fish Can You Keep In A 40 Gallon Tank?
If you plan on keeping fish in a 40-gallon tank, then you really are spoiled for choice! Here are all the different fish you can keep!
Guppies

Guppies are small, hardy fish that come in a variety of colors. They can be kept in a tank with other small fish and are a great choice for beginners.
Cory Catfish

Cory catfish are bottom-dwelling fish that scavenge for food. They are peaceful fish that can be kept with other small fish.
Cardinal Tetras

Cardinal tetras are schooling fish that come in a variety of colors. They are a popular choice for beginner tanks and can be kept with other small, docile fish.
Zebra Danios

Zebra danios are one of the most popular starter fish. They are hardy and can tolerate a wide range of water conditions. They are best kept in schools of six or more and can be housed with other small, active fish.
Neon Tetras

Neon tetras are one of the most popular aquarium fish, and for a good reason – they are colorful, hardy, and easy to care for. They prefer to school in large numbers and should be kept with other non-aggressive, small fish.
Mollies

Mollies are live-bearing fish that come in a variety of colors. They are an easy fish to care for but make sure you’re not keeping too many males together without females, as they will battle for dominance. Female mollies can be kept with other livebearing species or non-livebearing species such as platies or guppies.
Gouramis

Gouramis are tropical fish that come in a variety of colors. They prefer warmer water than some other species and like to have plenty of places to hide. Gouramis can be territorial, so make sure you’re keeping a mix of males and females.
Platies

Platies are live-bearing fish that come in many different colors, including calico, red, and black. They make good starter fish and can be housed with other livebearing species or non-livebearing species such as guppies or swordtails.
Endlers livebearers

Endler’s livebearers are small, live-bearing fish that come in many different color combinations. They are hardy and make good starter fish for those new to keeping aquariums.
How Much Gravel Do You Need For A 40 Gallon Fish Tank?
A 40-gallon fish tank will need about 35-40 pounds of gravel for a standard 1″ deep substrate. For deeper substrates, you may need more or less depending on the size and layout of your tank. Additionally, you’ll want to make sure that the gravel is the right type for your fish and plants – some may require a finer
Is A 40 Gallon Tank A Good Size?
Yes, a 40-gallon tank is an excellent size for a beginner aquarium. It’s large enough to give you plenty of space for decorations and plants, and it’s also large enough to keep some nice fish species, such as guppies, tetras, or Cory catfish. Plus, with the right filtration system and regular maintenance, it’s easy enough to keep clean and healthy.
Overall, a 40-gallon tank is an excellent starting point for anyone looking to set up a freshwater aquarium. With the right fish and equipment, you’ll have a beautiful setup that you can enjoy for years!
What To Consider When Stocking A 40 Gallon Fish Tank?
- One of the most important things to consider when stocking a fish tank is the waste load from the fish. The more fish you have in the tank, the more waste they will produce. This can be a problem if your filter isn’t up to par, as it may not be able to handle the increased load.
- Make sure you are using a filter that is rated for the size of your tank and that it is kept clean and in good working order.
- Another thing to consider is the swimming space required for each fish. Some fish need more room than others, and if they don’t have enough space, they may become stressed or even aggressive toward other fish. Make sure you are aware of how much swimming space each species needs, and plan your tank accordingly.

FAQ
Here are some frequently asked questions budding aquarists have about owning a 40-gallon tank!
How Many Tetras In A 40-Gallon Tank?
You can safely keep up to 20-30 small tetras in a 40-gallon tank. However, it’s always best to buy less than you need so that they have plenty of room to school and move around. (As long as you’re keeping a minimum of 5-6.)
How Many Platies In A 40-Gallon Tank?
You can typically keep up to 10-12 platies in a 40-gallon tank. As with all other fish, it’s important to make sure they have plenty of room to move around and swim, so you might want to add less than the maximum suggested amount.
How Many Goldfish In A 40 Gallon Tank?
It is not recommended to keep more than one goldfish in a 40-gallon tank due to the amount of waste they produce. More than one Goldfish will require a much larger tank (minimum 55 gallons) to thrive and live healthy, long lives.
How Many Mollies In A 40 Gallon Tank?
You can safely keep up to 10-15 mollies in a 40-gallon tank as long as you provide plenty of swimming space for them. Mollies are livebearers and will tend to breed if kept in large numbers, so it’s important to keep an even mix of males and females, or else the tank may become overpopulated.
How Many Cichlids In A 40 Gallon Tank?
You can safely keep up to 5-6 cichlids in a 40-gallon tank. Make sure you provide plenty of hiding spots and rocks for them to establish their territories and places to lay eggs. Cichlids are very territorial fish, so it’s important not to overcrowd the tank, or they may become aggressive toward each other.
It’s also important to make sure you’re housing more females than males. About 1 male for every 2-3 females is ideal.
How Many Guppies In A 40 Gallon Tank?
You can typically keep up to 15-20 guppies in a 40-gallon tank. However, it’s best to buy fewer than the minimum suggested amount to give them plenty of space to move around and socialize.
How Many Angelfish In A 40 Gallon Tank?
You can keep up to a pair of Angelfish in a 40-gallon tank as long as they have enough space to swim and establish territories. If you want more than a pair, then you’ll need a 55-gallon fish tank or larger.
Conclusion
A 40-gallon tank is a great size for anyone starting 5in the fish-keeping hobby. It can house a variety of different fish comfortably and provide years of enjoyment. Make sure to consider the amount of waste each fish will produce when stocking your tank, and use a filter that is rated for the size of your aquarium.
Also, make sure to give each fish enough room to swim and establish its own territory. With these things in mind, you’re on your way to setting up a beautiful and healthy freshwater aquarium!