The Best Guppy Stocking Level for a 20 Gallon Tank: Guppy Stocking Guidelines

How many guppies can you keep in a 20 gallon tank? The answer is complicated and depends on a variety of factors including the tank's setup, water quality, and whether or not you plan to breed the guppies. As a general rule of thumb, you can keep 8-12 guppies in a 20 gallon tank if the tank is heavily planted and has plenty of surface area. However, you may need to keep fewer guppies if the tank is less heavily planted or if you plan to breed the guppies.

To help you figure out the best stocking level for your 20 gallon tank, we've done a deep dive into the research of aquarium experts and experienced hobbyists. This research includes looking at recommendations for tank size, filter strength, surface area, and guppy behavior. By the end of this article, you'll know exactly how many of these beautiful, peaceful fish you can keep in your tank while ensuring their well-being based on your tank's unique setup and your goals.

Optimal Gender Ratios and Tank Mates

For a community guppy tank, the general consensus among experts is to keep a ratio of 1 male to 3 females. This helps prevent the tank from becoming overpopulated while ensuring that the males have enough females to display their natural mating behaviors. Too many males can lead to aggression and even the death of the females.

To keep male guppies from becoming aggressive, make sure the tank has plenty of hiding spaces, which can be provided by live plants and other decor. It is also important to keep the water quality high by performing regular partial water changes and using a strong filter to reduce stress, according to Aquarium Co-Op.

The best tank mates for guppies in a 20 gallon tank are other small, peaceful community fish such as tetras, rasboras, and corydoras catfish, according to FishLab. Corydoras are especially good tank mates because they are bottom dwellers and are compatible with guppies. Larger, more aggressive fish should be avoided.

When selecting tank mates, it is important to consider the temperament and adult size of the fish to avoid bullying or to prevent the guppies from being seen as prey. Guppies are known to nip at fish with long fins, so it is best to avoid fish with flowing fins, according to Aquarium Co-Op. Swordtails and platies are good options because they are livebearers and are close in size to guppies.

Avoid larger, territorial, or aggressive species such as cichlids, gouramis, or bettas that may harass or eat guppies. Also avoid fish that require different water parameters, such as goldfish, which prefer cooler water. It is important to keep the water parameters stable and suitable for the species you are keeping.

Water Parameters for Guppies

The water temperature should be kept between 74-82°F (23-28°C) to ensure that your guppies stay healthy, according to Micro Aquatic Shop and Hepper. Guppies also prefer slightly alkaline water, and their pH should be kept between 7.0-7.8 to promote their well-being and breeding, notes Light.fish and Aquatic Live Food.

When it comes to water hardness, guppies thrive in moderately hard water, with a general hardness (GH) of 4-12 and a carbonate hardness (KH) of 4-8, according to LiveAquaria. Guppies are sensitive to sudden changes in temperature and pH, so it’s important to invest in a reliable heater and check water parameters often.

Filtration and Water Change Routine

As noted by Aquarium Co-Op, the water change schedule for a 20 gallon guppy tank is usually 25-50% once a week. This ensures that the water quality stays high by removing waste and adding in fresh, dechlorinated water.

For filtration, Modest Fish suggests a hang-on-back (HOB) or canister filter that is rated for at least 40 gallons. This will ensure that there is enough mechanical and biological filtration to keep the levels of ammonia, nitrites, and nitrates down. Guppies are especially sensitive to poor water quality, so filtration is especially important.

In addition to the main filter, you can also add sponge filters to the tank to increase biological filtration. Since guppies produce so much waste, this will help increase the filtration capacity. Regular maintenance, including cleaning the filter media and doing partial water changes, will also help ensure that the water in the guppy tank stays healthy and the water parameters stay in the right range.

How to Breed Guppies

It can be hard to tell male and female guppies apart, especially when they're still fry. According to Pets on Mom.com, female guppies have a dark "gravid spot" near the base of the tail where the babies will develop when pregnant. While this spot can be hard to see in newborn fry, it will become more visible as the fish grow. Meanwhile, male guppies will develop a pointed anal fin called a gonopodium that's used for mating, while females will have a squared-off anal fin. This difference is easier to see if you wait until the fish are at least 2-3 weeks old.

To breed guppies successfully, Badman's Tropical Fish suggests separating males and females into different tanks or parts of the tank to avoid uncontrolled breeding and overpopulation. In addition, make sure that the breeding setup has plenty of dense live plant cover and hiding places to help the fry survive. If you're using a standard power filter, you may also want to add an air-powered sponge filter to the tank to prevent the fry from being sucked into the power filter. Finally, make sure that the water quality in the tank is good.

Live Plants and Lighting for the Guppy Tank

One of the first steps to creating a successful guppy tank is to add live plants. According to Modest Fish, some of the best low-light plants for a 20 gallon guppy tank are java moss, anubias, and java fern. These plants are all very hardy and easy to grow, and in addition to giving your guppies places to hide and making the tank look more natural, they can also help keep the water clean by absorbing excess nutrients.

In terms of lighting, the Buce Plant explains that LED lights are the best choice for a planted guppy tank. LED lights are energy-efficient and can be adjusted to meet the needs of the plants in the tank. The best lighting will have a good balance of red and blue light, with at least 50% of the light being red to ensure that the plants grow and develop good color.

To create a beautiful and practical planted tank, Aquarium Plants Forum recommends using driftwood or rocks as the focal point and then arranging the plants around them in a way that looks natural. Make sure to leave open spaces for the guppies to swim. In addition, you'll need to fertilize and prune the plants regularly to ensure that they stay healthy.

Wrapping Up: The Ideal Guppy Stocking Level for Your 20 Gallon Tank

The ideal guppy stocking for a 20 gallon tank is 12 fish - 4 males and 8 females. Maintaining stable water parameters is key to keeping guppies healthy and happy. A planted tank with good filtration and compatible tank mates is the best way to set up an environment for these colorful, active fish.

With the right care, guppies can live long, healthy lives and provide their owners with hours of entertainment.