Figure 8 Puffer Fish Species Profile

Characteristics, Origin, and Helpful Information for Hobbyists

Figure 8 Puffer - Tetraodon biocellatus
Figure 8 Puffer. Lee

Very few people can resist a pufferfish once they've seen one, and the small figure 8 puffer might be one you'd like to bring home to your own freshwater aquarium. Their expressive faces, intelligent curiosity, and propeller-like fins are charming. Pufferfish derive their name from their ability to inflate themselves with water or air when startled. This is a very successful defensive mechanism because it's harder to swallow a fish that's ballooning in size!

Species Overview

Common Names: Figure 8 puffer, eyespot pufferfish

Scientific Name: Tetraodon biocellatus

Adult Size: Up to 2 1/2 inches (6 cm)

Life Expectancy: 5 years

Characteristics

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

​​Origin and Distribution

The figure 8 puffer originates in the brackish (partial salinity) streams and estuaries of Southeast Asia, including Borneo, the Malaysian peninsula, Sumatra, and Thailand. Although these fish do not breed in captivity, they have not as yet been overfished for the trade and are not considered to be a threatened species. Figure 8 puffers in home aquariums have all been wild-caught, which means it's important for them to be quarantined when they first arrive. Be sure new puffers cannot pass along illness to other fish.

Colors and Markings

figure 8 pufferfish GIF
Illustration: The Spruce / Lara Antal

Reaching an adult size of fewer than three inches, Figure 8 puffers are small for pufferfish. They are deep brown in color on the upper portion of the body with 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 fish, many of which resemble the shape of a figure 8.

Even when not startled, all 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 get 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.

Tankmates

Puffers are not well suited to a community tank because they tend to be aggressive. Ideally, figure 8 puffers should be kept alone or in a large aquarium with only a few other fish that thrive in the same partial-salinity 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. As a rule of thumb, don’t expect to successfully keep them in a typical freshwater community tank.

Aggressive

Even puffers that have previously been docile and tolerant can become aggressive as they age, and if they are insufficiently fed. A puffer can turn on its tankmates and chew them to pieces.

Figure 8 Puffer Habitat and Care

Controversy exists over whether any puffers are actually true freshwater fish. They originate in the fresh waters of Southeast Asia, 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 comparative lifespans in captivity when housed in different salinities.

Filtration should be robust, as figure 8 puffers tend to create a lot of debris when 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 and listless. As a result, they require ample open space to swim, but they also need places to both hide in and explore. They can be hard on plants, due to aggressively attacking their foods; pieces of food rain down 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 and Feeding

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

Because the nutcracker-like beak of the figure 8 puffer can become overgrown, it is important to include plenty of very hard-shelled foods in their diet to keep the teeth ground down. Tetraodon snails or pond snails are terrific for this purpose. 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.

Gender Differences

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

Breeding the Figure 8 Puffer

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

More Pet Fish Species and Further Research

If you’re interested in a similar species, check out this other brackish water puffer:

Check out additional fish species profiles for more information on other freshwater fish.