Figure 8 Puffer Fish

The Unique Tetraodon Biocellatus

Figure 8 Puffer - Tetraodon biocellatus
Figure 8 Puffer. Lee

Very few people can resist a pufferfish once they've seen them, and the small figure 8 puffer might be one you'd like to provide with a home in your own freshwater aquarium. Their expressive faces and propeller-like fins are charming. Pufferfish derive their name from their ability to inflate themselves with water or air when startled. It's a defensive mechanism—it's harder to swallow a large fish than a small one.

Breed Overview

Common Names: Figure 8 puffer, eyespot pufferfish

Scientific Name: Tetraodon biocellatus

Adult Size: up to 2 1/2 inches (6 centimeters)

Life Expectancy: 5 years


Family Tetraodotidae
Origin Freshwaters of Southeast Asia
Minimum Tank Size 15 gallons
Diet Live foods, prefer snails and shellfish
Breeding Egglayer
Care Intermediate
pH 7.0–7.5
Hardness 5–12 dGH
Temperature 72–79 F (22–26 C)

​​Origin and Distribution

The figure 8 puffer originates in freshwaters and in brackish streams and estuaries of Southeast Asia, including Borneo, the Malaysian peninsula, Sumatra, and Thailand. Pet figure 8 puffers are usually wild-caught, which means it's important for them to be quarantined when they first arrive to be sure they don't pass along illness to other fish.

Colors and Markings

figure 8 pufferfish GIF
Illustration: The Spruce / Lara Antal

Figure 8 puffers are small for pufferfish, reaching an adult size of fewer than 3 inches. They are deep brown in color on the upper portion of the body and white on the underside. Yellow spots and lines are sprinkled throughout the body. The name is derived from the markings on the back of the puffer that resembles a figure 8.

Even when not startled, figure 8 puffers have a roly-poly appearance. You can easily spot a well-fed puffer by its rounded belly. Puffers have two pairs of teeth, each of which is fused together, giving it a beak-like appearance. This unusual arrangement of teeth gives it the ability to crush hard materials such as the shells of crustaceans. These teeth grow throughout the life of the fish and must be ground down to keep them from being too long. For this reason, they need hard-shelled foods to help keep their teeth the proper length.


Puffers are not well suited to a community tank because they tend to be aggressive. Even puffers that have previously been docile can become aggressive as they age, or if they are not well fed. A puffer can turn on its tankmates and chew them to pieces. On the other hand, most owners have found figure 8 puffers more peaceful than any other puffers and some have successfully kept them in a community tank.

Ideally, figure 8 puffers should be kept alone or in a large aquarium with only a few other fish that thrive in the same habitat. Owners who have kept them in brackish water find that bumblebee gobies, knight gobies, and mollies are suitable companions. Owners keeping them in freshwater aquariums have reported keeping them with fish such as barbs, sharks, and tetras. In these cases, the habitat may have allowed sufficient space to keep the puffers from feeling threatened. As a rule of thumb, don’t expect to successfully keep them in a typical freshwater community tank.

Figure 8 Puffer Habitat and Care

Controversy exists over whether any puffers are actually true freshwater fish, but some people believe figure 8 puffers fall into that category. They originate in the fresh waters of the Southeast Asia region, and although they tolerate brackish or even full saltwater, they may fare better in freshwater. Others have reported the opposite, stating that salinity in the range of 1.005 to 1.008 will significantly extend the lifespan of the figure 8 puffer. Scientific data is lacking on the lifespan during captivity in freshwater.

Figure 8 puffers prefer a neutral pH and tolerate soft to moderately hard water. Keep the water temperature on the warm side, around 78 F. The minimum tank size should be 15 gallons for a single specimen, more if possible. Filtration should be robust, as figure 8 puffers tend to leave a lot of debris from eating. They are sensitive to ammonia, nitrites, and nitrates, and will not do well in a tank that is still going through the start-up cycle. Frequent water changes to maintain pristine water conditions are recommended for this fish.

Unlike most fish, Figure 8 puffers are able to recognize and respond to their owners, but they can also get bored. As a result, they require ample open space to swim, but also need places to hide and explore. They can be hard on plants, due to aggressively attacking their food, which often falls on plants and other aquarium décor. Decorate the tank with sturdy plants, and be aware that you may need to replace them from time to time.

Figure 8 Puffer Diet

The dietary needs of figure 8 puffers are perhaps one of the more demanding aspects of keeping this fish. Flake or dried foods do not meet their dietary needs. Instead, they must be fed meaty and hard-shelled foods such as clams, crayfish, crickets, daphnia, krill, mollusks, oysters, plankton, scallops, snails, shrimp, and worms.

Because the beak of the figure 8 puffer can become overgrown, it is important to include plenty of hard-shelled foods in their diet to keep their teeth from overgrowing. In nature, they typically eat crustaceans. Although live foods are ideal, some owners have had success training their puffer to eat some frozen foods. Be sure to select high-quality frozen foods.

Sexual Differences

Even for experts, it is nearly impossible to sex figure 8 puffers. The most certain way to sex them is to see the female lay eggs, which is an extremely rare occurrence. Only a few cases of spawning in captivity have been reported.

Breeding the Figure 8 Puffer

Little is known about how to breed figure 8 puffers. On the rare occasions they have spawned in captivity, they have laid eggs on a flat surface, such as the substrate. The male guards the fish for approximately a week until the fry are free-swimming.

More Pet Fish Breeds and Further Research

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Otherwise, check out all of our other freshwater and saltwater fish profiles.