The figure 8 puffer fish, also known as dichotomyctere ocellatus or the eyespot pufferfish, is one of the smallest and most attractive brackish water tropical fish available to fish keepers.

Aquarists prize them for their small size, big intelligence, and comic antics.

If you have mastered the proper care of brackish water aquariums the figure 8 puffer can be easy to care for. But there are things you need to know both before and after you add them to your tank so you can have healthy fish that live more than a decade.

Keep reading for more information on the care, maintenance, and breeding of figure 8 puffers.

Stats

Tank sizes listed are the minimum.
Size: To three inches
Tank: 10 Gallons
Strata: Bottom
PH: 7.8 to 8.3
Hardness: Soft to medium. dH range: 5-12
Salinity: 1.005 and 1.008 specific gravity [SG]
Temperature: 80 F-85 F (26 – 30 C)
Order: Tetraodontiformes
Family: Tetraodontidae
Genus: Dichotomyctere
Species: D. ocellatus

Origin and Appearance

Figure 8 puffers are native to the brackish tidewaters of Southeast Asia from the lower reaches of the Mekong River in Cambodia to the coasts of Thailand, Malaysia, and Borneo.

Sometimes called the freshwater figure 8 puffer, the name is misleading as figure 8 is not adapted for long-term survival in purely freshwater. This is a species that, while it can live in freshwater for an extended time,  thrives in water with some salt content.

Almost all of the figure 8 puffers sold in the aquarium trade are wild-caught fish. They are considered one of the most beautiful puffers because their bright coloring does not fade or change appreciably over time.

It may not be the largest puffer but what it lacks in size, it makes up for in coloring. It is sometimes called the eyespot puffer because of the two dark circles or eye spots in front of its eyes.

In color, the figure 8 puffer is olive to dark olive on its back, shading to a yellowish or white belly. Over this is a pattern of bright yellow rings and partial rings. The fish’s darker background color makes the yellow stand out vividly. Often these rings and lines connect to form a figure 8, where the species name comes from.

It is practically impossible to tell male and female fish apart. This is one of the reasons you rarely see bred fish.

Its body shape is pure puffer with a wedge shape ending in a broad, flat tail. Figure 8 puffer fins appear oversized on their small body. This gives them amazing maneuverability and the power for short bursts of speed.

Some compare its ability to move to a helicopter for the way they hover and turn. Like puffers in general, the figure 8 puffer is an intelligent fish that loves to explore its environment. They can learn your presence and will interact with you. Some keepers train their fish to feed from their hands.

Be careful when doing this with figure 8 puffers. They can’t always tell your finger from a bit of shrimp, and you might get a good nip! Figure 8 puffers have teeth. In the wild, they feed on clams and snails, which keeps tooth growth in check. In captivity, they must have shelled fish in the diet, or their teeth can grow out of control.

The Figure 8 puffer size can be up to 3 inches.  In captivity, they can live up to 18 years of age, longer than many four-legged pets.

Care

The figure 8 puffer is a species where it is critical to know how the fish has been kept before introducing it to your aquarium. You always want to start with quality stock.

As a wild-caught fish that can pass through several hands before it winds up in a tank in your fish store, the condition of the fish you buy can be suspect.

If you buy your figure 8 from a pet store, examine the fish carefully for signs of the following:

  • Nipped fins
  • Bite marks from other fish
  • Ich
  • Other fish fungus
  • Sluggish behavior
  • Starved or skinny looking fish

Fish that show some signs of bullying, like nipped fins, but are otherwise actively swimming in the tank and appear full-bodied, are worth taking home.

If you buy your fish online, make sure you trust your reseller and that they guarantee the health of the fish they sell to you.

– Tank Size and Water Conditions

A healthy fish deserves a good, healthy aquarium. Puffers like to roam in their fish tanks, so a 10 gallon, horizontal format aquarium is an ideal size for one fish. If you want to keep tank mates with your figure 8 puffer, a 20-gallon aquarium is a better size.

If keeping multiple puffers, allow 10 gallons per puffer. If you are going to keep your figure 8 puffer with tank mates, you will also need a quarantine tank to house the fish for a few weeks until you are certain it is healthy and disease-free.

While figure 8 puffers can tolerate differences in salinity, the two areas critical to their health are water temperature and water cleanliness.

Figure 8 puffers are warm-water fish. Their ideal temperature range is 80 F-85 F (26 – 30 C). It is hard to keep water in this temperature range without a good aquarium heater.

A good filtration system is also a must. The coastal waters these fish live in are constantly refreshed by changes in the tide. They are very sensitive to contaminants in the water, such as ammonia from fish waste.

Filtration combined with regular cleaning helps keep their water fresh. A good filtration system also moves warm water around and helps keep the temperature even throughout the tank.

External canister-type systems are preferred. Puffers will root around the bottom and could nip or chew on the filter media and lines.

Most fish keepers do not have access to seawater, so marine mix is added to de-chlorinated and conditioned tap water. Follow the instructions that come with your brand of additive to get a salinity of 1.005 and 1.008 specific gravity [SG]. This is a good, mild level of salinity that most brackish water fish will tolerate well.

Frequent water changes are important. Changing 15 percent weekly or 30 percent biweekly will keep your habitat nice and clean. Use siphon-type cleaners to get out larger food waste and to clean up the shell litter that can accumulate from feeding puffers.

Aquascaping is important for puffers. They need a variety of things to explore in their environment.

A two or three-inch sand or gravel substrate is a good start. Rooted plants can be a problem with puffers. They could dig them up. Floating plants that can tolerate brackish water look good do not bother the puffers and could be beneficial for tank mates.

Rocks and hardscapes with nooks and crannies are perfect for figure 8 puffers. Size the openings for a three-inch fish, and they will explore it.

In addition to regular feeding, if you drop clamshells in the tank, the figure 8 puffer will chew on them. This will help control their tooth growth.

With figure 8 puffers, the larger and more visually complex the habitat is, the greater likelihood you have of the fish being tolerant towards tank mates.

– Diet

Figure 8 puffers are easy to feed. They like meaty foods, living or dead. This makes feeding them easy. In the wild, they feed on a variety of fish, clams and mussels, crabs, snails, and other marine life.

Any and off of these are good choices for your figure 8 puffer. If you can find a way to sneak the crabs, shrimp, or crayfish into the tank, your puffer will hunt them and get some mental stimulation in the process.

If not, chopped meaty foods work just as well. Limit feedings to once a day, and be sure to not let food waste decay.

– Tank Mates

Figure 8 puffer compatibility is easier to figure out than larger puffers. It is considered on the friendly end of the behavior spectrum. This is not to say that it cannot be territorial or even antisocial.

If you want to keep your figure 8 puffer with tank mates, it is best to start with as young of fish as you can find. This is especially true if you want to have more than one figure 8 puffer in the tank. While adult fish will fight, sometimes to the death, for territory, fish that have been raised together often will not.

A tank with lots of things for them to explore keeps their mind off other living things in the tank. If they get bored, figure 8 puffers will go exploring with their teeth.

As you learn your fish’s attitude, it will help you determine what you can or should not have as tank mates for them.

Some keepers will use species of gobies as tank mates. This can work if the tank is large enough for the gobies to have places to hide. If not, the puffer will harass and eventually kill them.

Mollies are good choices for figure 8 puffer tank mates. They are peaceful, keep to themselves, do well in brackish water, and are close to three inches at adulthood.

The downside to mollies is that they can produce a lot of fish waste. Keeping the tank well-cleaned is doubly important.

Mono Fish (Monodactylus) can do well in tanks with figure 8 puffers. They grow to be quite a bit larger, up to 11 inches, so you need a very large aquarium to house a school of six. They do best in schools and will not bother the figure 8 puffer.

Species to avoid include large, aggressive fish who will pick on the puffer. Also, snails and shrimp will just wind up on your figure 8 puffers dinner table. If your figure 8 puffer is not the friendly type, you may have to keep it in its solitary tank.

Don’t be surprised if the fish sees you coming and swims to the front of the tank to greet you.

Breeding

Figure 8 puffers are a poor choice for captivity breeding because there is no good way to tell males from females, and little is known about how to recreate their breeding habits.

Breeding has been seen in the wild. Figure 8 puffer males create shallow nests in the bottom and court females to lay their eggs. There are very few reports of female figure 8 puffers laying eggs in an aquarium.

With so little known about how to entice them to breed, most keepers just purchase their fish and focus their efforts on providing good homes for them.

Conclusion

  • Figure 8 puffers reach three inches in size and can live up to 18 years.
  • Their teeth are constantly growing. They need a diet heavy in clams to help keep that growth in check.
  • These fish need brackish water to thrive.
  • A visually stimulating tank will keep them entertained and less likely to threaten tank mates.
  • Plan on 10 gallons per fish, 20 gallons if you are including tank mates.
  • Quarantine all new fish before adding them to home aquariums.
  • Feed them meaty foods to keep them healthy.

Very few people are willing to do the work required to care for and maintain brackish water fish. But if you are interested in puffers, go ahead and keep them in your aquarium. You will be rewarded with a personable pet fish that gives you joy for years to come.

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