How Many Guppies in a 30-Gallon Tank Is Recommended?

Sharing is caring!

Guppies (Poecilia reticulata) are brightly colored, active pet fish that are easy to keep and breed, making the “Millionsfish” or “Rainbowfish” a popular choice for many freshwater tropical tanks.

These beautiful livebearers are incredibly prolific breeders, so you can rapidly finish up with many more fish than you started with!

That’s no problem if you have a large tank, but not such good news if you keep a smaller setup.

But how many guppies can you keep in a 30-gallon fish tank? Read this guide to find out!

How Many Guppies Can Live in a 30-Gallon Aquarium?

In a medium-sized 30-gallon tank, you can comfortably keep up to 15 adult guppies.

However, the number of fish you can keep depends on a couple of factors, including the guppies’ sex and the size of the variety you have.

Overcrowding Causes Stress

It’s extremely important that you don’t overcrowd your tank with too many fish!

Overcrowding causes severe stress in all freshwater aquarium fish species, including guppies. When a fish is stressed, the creature’s immune system is compromised. That leaves the fish weakened and vulnerable to attack by bacteria and parasites.

Bottom line: don’t be tempted to cram too many fish into your aquarium!

Aquarium Stocking Calculation

You can work out how many freshwater fish your aquarium can safely accommodate by using the following simple calculation.

  • Allow 1 inch of fish per 1 gallon of water.

However, this calculation takes a somewhat broad-brush approach, as there are a few factors you should take into account when stocking your aquarium with guppies, including:

Fish Size

Male guppies grow to an adult size of between 1.3 and 1.6 inches long, while female fish are usually a little larger, measuring 1.3 to 2.5 inches long.

So, in theory, you can keep a maximum of 15 2-inch guppies in a 30-gallon tank.

Gender Mix

As previously mentioned, guppies are prolific breeders, hence their common nickname of “Millionsfish!”

Basically, if you provide your guppies with optimal tank conditions and a varied, high-quality diet, they will constantly reproduce.

Of course, if you have a community tank that’s home to omnivorous or carnivorous fish, many of the guppy fry will be eaten. However, some usually survive, potentially leading to overcrowding issues.

Now, all that breeding is extremely stressful for the female fish, who are constantly harassed by amorous males. In fact, the stress of courtship, pregnancy, and giving birth considerably shortens the female guppy’s lifespan.

For that reason, we recommend keeping one male guppy to three female fish. That provides a good balance of the sexes and prevents the females from being hassled and stressed too much.

Rainbow Fish!

Male guppies are considerably more beautiful than females. It’s the male guppies that have the vibrant colors and fancy tail forms that give the species the name “Rainbowfish.”

So, with that in mind, you might prefer to keep only male fish.

However, although guppies are generally peaceful fish, male guppies can be territorial and aggressive without female fish in the mix to distract them.

So, to maintain a harmonious tank, we recommend keeping a combination of these popular freshwater aquarium fish in the ratio given above.


As mentioned above, male guppies can be highly territorial, so keeping them in a spacious tank with plenty of decoration and the right mix of females is the best way to avoid problems.

However, if you keep other types of fish in your community, you need to take into account their behavior.

For example, if you have territorial fish in your collection, you’ll need to allow more space to prevent disputes and fighting between individuals. If you keep shoaling fish, you must ensure they have plenty of open swimming space.

Tank Decoration

The rule of thumb “inches of fish per gallon of water” calculation mentioned above doesn’t take into account how much space in your tank is taken up with decorations, plants, substrate, etc.

So, if you have a 30-gallon tank with a couple of inches of gravel on the bottom, masses of thick, bushy plants, and lots of driftwood, your 30-gallon capacity is considerably reduced.

Therefore, when working out how many fish you can keep in your tank, you’ll need to take all those things into account.

Guppy Varieties

Did you know that there are over 50 varieties of guppies?

Many of these variants are created through selective breeding to get the most unusual patterns, vivid colors, and tail types.

Often, if you keep a community tank containing many different fish species, you’ll find that catering to different dietary and habitat requirements can be challenging.

However, the different guppy species all share the same basic care requirements, and that means you can easily create a truly spectacular setup containing only guppies.


Wild guppies generally live for around two years. In captivity, the fancy guppy has a lifespan of between two and five years.

How To Keep Guppies

How Many Guppies in a 30 Gallon Tank

Now that you know how many of these beautiful fish you can keep in your 30-gallon tank, here’s a brief overview of what guppies need to thrive.

Water Parameters

Guppy fish need an ideal water temperature of between 72° and 82°F, a pH level in the range of 6.8 to 7.8, and a water hardness of 8 to 12 dGH.

The levels of ammonia and nitrites in the water should always be zero, and nitrates should be below 20 ppm.

Guppies can also tolerate and do well in a blackwater aquarium community setup. You can read more about setting up a blackwater tank in the article at this link.


To keep your guppy tank water healthy and clean, you need to run an efficient filtration system to remove pollutants from the water.

Guppies don’t appreciate too much movement of water in their environment since the rivers and water bodies they come from are shallow and slow-moving.

We recommend using mesh to protect the filter inlet pipe to prevent tiny juvenile guppies and fry from being sucked into the filter unit.

Tank Decoration

Guppies are not particularly shy fish when kept in groups.

However, like many small fish species, they do appreciate having a few hiding places in their tank where they can take refuge if they feel threatened by larger fish.

Female guppies will also appreciate somewhere to hide from overenthusiastic males.

We recommend including plenty of driftwood, smooth stones, and caves as decoration in your guppy tank.

If you want to keep a single-species guppy tank, a large piece of Dragon stone decorated with surely anchored aquatic plants makes a fabulous centerpiece.


Plants are essential additions to a guppy tank.

Although these are not especially shy fish, their myriad fry will need somewhere to hide until they are large enough not to be eaten by either their parents or other adult fish in the aquarium.

Dense, bushy plants can provide the perfect hideout for guppy fry!


Guppies are diurnal fish. That means they are most active during the daytime when the sun rises.

In captivity, you need to replicate that by providing lighting for the fish from morning through to evening. Living plants also need eight to ten hours of light each day to photosynthesize.

If you’re not around to manually switch the lights on and off each day, we recommend upgrading your aquarium lighting unit to one with an automatic timer feature.

Alternatively, you could use a cheap auto-timer plug that you’ll get from good DIY or homeware stores.

Regular LED lighting is fine for a guppy tank.

Tank Maintenance

All fish tanks need regular maintenance to keep the environment safe and healthy for your fish.

Once a week, use an aquarium vacuum cleaner to remove organic waste from around the bottom of the tank, especially in the corners and around plant bases. You can also use an algae magnet or scraper to remove algae from your viewing panes.

For your filter unit to work properly and to ensure good water movement through the tank, you need to rinse the filter media in tank water every couple of weeks.

That process helps to remove sludge from the media, filter box, and around the impeller.

Replace the filter media every so often, in line with the manufacturer’s directions.

Diet and Feeding

Guppies have upturned mouths, which means they are primarily surface feeders. In the wild, guppies enjoy a diet of water-bound insects, mosquito larvae, algae, and some plant matter.

Captive-bred guppies will eat pretty much any form of commercial fish food.

A good basic daily diet for guppies should comprise some tropical fish flakes supplemented with frozen foods, such as bloodworms, daphnia, mosquito larvae, and the like.

Live Foods?

Although your guppies will happily eat live foods, I prefer to feed my fish frozen meaty foods instead.

Unfortunately, live foods can contain bacteria and parasites, which can be very harmful to your fish. So, unless you have a reliable supplier or you run a home brine shrimp hatchery, live foods are best avoided.

Never take live foods from the natural environment!

Health and Disease

Guppies are quite hardy fish that can reach their five-year life expectancy if properly cared for. However, there are a few diseases that can affect guppy adults and fry, including:

The best way to prevent diseases from getting into your 30-gallon guppy tank is to ensure that the water is clean and provide the fish with a high-quality diet.

When buying new fish, always keep them in a quarantine tank for at least two weeks before introducing them to your main display aquarium with your guppies.

That gives you the chance to spot any diseases or pests and treat them accordingly rather than risk infecting your whole main tank.

Plants can carry diseases and parasites, too! So, it’s a good idea to inspect new plants carefully for snails, flukes, etc., and rinse them in a weak antibacterial solution to kill anything nasty before it gets into your tank.

Availability and Price

Guppies are readily available at most pet and fish stores and via online suppliers and breeders.

These beautiful little fish are surprisingly expensive, with prices starting from around $10 for a single fish! Rarer variants and those with the most unusual colors and patterns are even pricier.

However, you can often get good deals if you buy a group of guppies.

Final Thoughts

Did you enjoy our guide to how many guppies you can keep in a 30-gallon fish tank? If you did, please share the article before you go!

Guppies are gorgeous, brightly colored little fish that are extremely popular in the hobby. In a 30-gallon aquarium, you can keep up to 15 guppies without the tank becoming overcrowded.

Do you keep guppies? What size tank do you have, and how many Millionsfish live in it? Tell us in the comments box below.

Sharing is caring!


Apparel & Accessories

Beds & Furniture

Cameras & Monitors




Health Supplies

Aquarium Pumps

Aquarium Filters

Aquarium Lights

Aquarium Heaters

A Dog-Loving Resort Manager Rescues Canines in Need
8 Den-tastic Dental Health Tips for Puppies!
Dogo App Review 2024: An Expert Breakdown
Everything You Need to Know About Osteopathy for Dogs and Cats
Funny Cats | Funny Ski Fails
Cake Decorating 101 with Funny Dog Maymo: Yummy Cake Recipe by Dog Chef
Adorable Pets You’ll Just Fall In Love With! Funny Pet Videos 2019
Cat Fails – Funny Cat Videos – Funny Animal Videos 2020