Here are the tank size recommendations for guppies:

Tank size (gallons)Number of guppies
5 gallons3
10 gallons5
20 gallons10
25 gallons12
30 gallons15
40 gallons20
55 gallons23
75 gallons37
90 gallons45

The rule of thumb is to have 1 gallon of water for every inch of guppy fish. Male adults are about 1.4 inches long while females are about 2.4 inches. It is ideal to keep 1 male for every 2 females, otherwise, keep males and females separately if the tank is small.

Tank Size Recommendation for Guppy fish

Guppy Fish Tank Size

An overcrowded tank can lead to breathing complications in fish and encourage the quick spread of diseases. Here are stocking guidelines and recommendations:

  • You need one gallon of water for every inch of guppy fish.
  • Adult guppies are 1.4 – 2.4 inches long, so the ideal stocking recommendation is about 2.5 gallons of water per guppy fish.
  • Males are smaller than females, meaning you can stock slightly more adult male guppies than females in the same volume of water.
  • The ratio of females to males should be 2:1.

How many guppies in a 5-gallon tank?

You can keep two to five guppies in a 5-gallon tank depending on their size and gender. The tank is enough for only two female guppies or 4-5 males if you’re experienced and can keep the tank well-cycled.

A 5-gallon tank is the minimum tank size recommended for keeping guppy fish.

Guppies are schooling fish, so I recommend keeping at least two in the same tank to encourage them to play and swim together whenever they feel unsafe.

A 5-gallon tank is enough to keep the guppies from birth till adulthood when they are grown to 2 inches long. The tank is small and easy to clean and maintain for beginners.

Pro tip: Do not place the guppies in direct sunlight because five gallons is more susceptible to temperature changes. High temperatures can reduce oxygen in the water and encourage the growth of algae. 

10-gallon tank

A 10-gallon tank can accommodate up to five guppies. You can keep about 4 female guppies or up to 7 males. However, if you’re mixing them up, stock 3 females and 1 male. More males in the tank will stress the female guppies too much.

A 10-gallon tank is not recommended for breeding guppies because it’s still quite small to accommodate adult guppies and guppy fry. The fish would compete aggressively for space and oxygen.

Besides, adding decorative substrates and plants in a ten-gallon is difficult without reducing the number of fish to keep in the tank.

20-gallon tank

A 20-gallon fish tank can accommodate up to ten guppies. The guppies will swim freely and play without knocking and injuring each other. The oxygen supply inside the water is also steady, keeping the guppies active and healthy. 

If you want to breed guppies for a start, use a 20-gallon tank. In that case, female guppies should be more than male guppies inside the tank.

Start with one male and two female guppies or more in the tank. As the guppies reproduce, their population will double in just two months. At that point, you will need a larger tank for your guppies. 

With a 20-gallon tank, you can decorate the tank with some aquarium plants, rocks, and pebbles to provide good hiding, playing, and breeding spaces for guppies.

25-gallon tank

There is no significant difference between a 20-gallon fish tank and a 25-gallon tank. However, the five additional gallons can hold some extra guppies. Keep between 10 and 12 guppies in a 25-gallon tank.

A 20-gallon tank is suitable for breeding guppies, but you will need a bigger tank to accommodate the young guppies. Otherwise, the fish will be overpopulated, and the water will not be enough to provide adequate oxygen for all the guppies.

Decomposing fish food leftovers also contribute to ammonia build-up in the aquarium and can kill all guppies in the tank quite fast. Change 50% of the water every week and wipe out any dirt from the 25-gallon tank using a clean cloth. Most importantly, remove any fish food leftovers to prevent them from decomposing inside the tank. 

30-gallon tank

A 30-gallon tank can accommodate 15 guppies or less. The remaining space is enough for your guppies to breed and dwell. 

A 30-gallon tank is also large enough for breeding guppies. You can start with two males and four females in the tank and let them breed to fill up the aquarium.

Since guppies give birth every month, your aquarium will be full in two to three months, and there will be no more space for breeding.

A 30-gallon is much heavier with many guppies, and it needs proper care to keep the fish healthy. Change 30% to 40% of the water every week and clean the tank.

40-gallon tank

Keep 20 guppies or less inside a 40-gallon tank.

Use a 40-gallon tank to breed guppies or decorate your home and office spaces. As the population of the guppies increases, you can transfer some to another tank.

Unlike the smaller tanks, a 40-gallon tank can accommodate more than one aquarium plant. 

Promote oxygen circulation using an aquarium filter and change 30% of the water twice a month.

55-gallon tank

A 55-gallon tank is huge, and it gives the guppies plenty of space to thrive. You can use the tank to breed guppies and add multiple aquarium plants and substrates of your choice. Keep 27 guppies in a 55-gallon tank and add plenty of plants and hiding places in the tank.

Some of the best aquarium plants for a 55-gallon tank include Java moss, Java fern, and Moneywort.

Change 30% of a 55-gallon tank twice a month. That will give guppies a clean and healthy environment to thrive. I also recommend an aquarium filter for such a tank.

65-gallon tank

A 65-gallon tank can accommodate 32 guppies if you don’t add many decorations. If you decorate it heavily, keep less than 32 guppies in the tank.

The tank is spacious enough for breeding guppy fish. Guppies are not aggressive, so you can keep other fish with them in such a big tank.

Before putting fish of different species together, make sure they cannot prey on each other, and that both fish share the same water conditions.

Because of its size and weight, cleaning and maintaining a 65-gallon tank can be challenging. Generally, change 25% of the water every week and clean any dirt and food debris accumulated in the tank.

75-gallon tank

A 75-gallon tank is big enough to hold up to 34 guppies without decorations inside the tank. Try keeping guppies with their compatible tankmates such as platy and mollies in a 75-gallon tank.

A 75-gallon tank also requires fixed structural support to be stable.

Clean and prune the aquarium plants and substrates every month. Also, change 25% of the water every month without removing the fish. Having an aquarium filter is an added advantage.

Minimum tank size for guppies

The minimum tank size for guppies is a 5-gallon tank, which can house 2-5 guppies. Ideally, you can keep only two females in the tank or 2 females and one male guppy.

Alternatively, you can keep 3-4 male guppies in a 5-gallon tank, but this should only be left to experienced fish keepers.

Signs your aquarium is overcrowded with guppy fish

An overstocked guppy tank can mean some of your fish go without food for long periods. They become weak due to the inability to compete for other resources and may be picked at by stronger, bigger fish.

Here are some signs that your aquarium is overcrowded with guppy fish.

Your guppies are dying

If you notice your aquarium fish dying without a particular reason, you want to start by fixing the tank size to ensure your stocking is done correctly.

Besides that, you want to ensure oxygen and other supplies are enough for your fish to prevent them from dying overnight.

Guppies gasping at the top of the tank

Overcrowding increases competition for oxygen while the accumulation of ammonia increases too.

These will make the fish gasp at the top of the tank to reach for oxygen.

In fact, if you notice your guppies swimming at the top of the tank most of the time, it is likely that they are overstocked.

Increased ammonia level in the tank

Guppy waste and food leftovers contaminate aquarium water. When you measure ammonia levels in your aquarium and it is more than zero, that is a sign of an overcrowded tank.


I recommend keeping a maximum of 3 guppies in a 5-gallon tank (2 females and 1 male). You can stock up to 5 guppies in a 10-gallon tank, 10 guppies in a 20-gallon tank, 15 guppies in a 30-gallon tank, 27 guppies in a 55-gallon tank, and 37 guppies in a 75-gallon tank.

Keep the water clean and well-cycled. Additionally, when keeping male guppies alone, use the 10-gallon tank or more to accommodate more guppies with fewer territorial issues.


Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *