Pufferfish are known for their fun and boisterous personalities in the aquarium hobby, making the figure 8 puffer a popular choice for beginners and more advanced hobbyists.
This smaller species of puffer is extremely popular and can bring life and excitement to tanks that might not have a large floorplan. Though their size requirements are minimal, these fish can be more difficult for beginner hobbyists due to their brackish tank and dietary requirements.
Keep reading to find out everything you need to know about figure 8 pufferfish, what water conditions they need, and how to keep one of these entertaining fish in your aquarium!
Note: Figure 8 puffers belong in brackish tanks. If you’re looking for a freshwater fish, check out our guide on strictly freshwater pufferfish species here.
The figure 8 puffer has many names, both scientific and common ones.
These fish will usually be labeled as figure 8 puffers in pet stores, but you might also see them for sale as figure eight puffers or eyespot puffers.
Scientifically, things get a little more confusing. Tetraodon biocellatus, though technically outdated is still how they are usually classified even though they have been moved to Dichotomyctere ocellatus.
Now, there are only six species in the Dichotomyctere genus, including fresh- and brackish water species from South and Southeast Asia.
Not much is known about the figure 8 fish’s natural habitat, which is why there is some controversy about how these puffers are best kept within in the aquarium hobby.
These fish have been studied in the Mekong River throughout Cambodia, as well as in Malaysia and Indonesia. There, they prefer calm waters in estuaries, mangrove forests, and small streams.
As we’ll discuss later, it has not fully been determined yet if the figure 8 puffer is a freshwater or brackish water puffer; like other species in areas of rivers that are close to saltwater, these puffers probably migrate to different salinities based on seasons and mating.
However, because the Mekong River meets and mixes with the Gulf of Thailand and the South China Sea, it’s likely that these puffers mostly occur in mainly brackish waters.
With a maximum size of around 4 inches (10.2 centimeters), figure 8 puffers stay relatively small.
Their appearance is quite striking and earns them their name. These fish have a creamy white belly, yellow body, and black markings. Their common name, figure 8, is derived from the eight-shaped marking on their heads.
Like other puffers, the figure 8 has a beak mouth that allows them to crush through shells and other invertebrates. Interestingly, this fish can close and blink its eyes, which arguably adds to its curious pufferfish personality!
Figure 8’s are sometimes confused with young Ceylon puffers (Tetraodon fluviatilis) or green spotted puffers (Tetraodon nigroviridis), though you can tell the difference by looking at the shapes and concentrations of their black spots or bands.
If you’re really having difficulty telling these species apart, make sure to go to a reputable seller that can tell you their scientific names.
How long do figure 8 puffers live?
Though small, these feisty fish can last a long time. Surprisingly, these little puffers can live to be 15 years old!
Unfortunately, because their exact needs aren’t entirely known and, therefore, rarely met, many aquarium fish do not make it to this age.
Figure 8 puffer tank requirements
Although they’re one of the easier puffer species to keep, figure 8 puffers (and most pufferfish except for the tiny dwarf puffer) are not a great choice for beginner aquarists, as they require relatively specific care.
For a single figure 8 puffer, an aquarium of at least 30 gallons (113.6 liters) or a 20-gallon (75.7 liters) long tank is required. These puffers need heavy filtration, as they produce a lot of waste and are messy eaters.
One of the trickiest parts of owning these fish is getting the water chemistry right, which we will discuss later.
Like all puffers, figure 8’s are very easily bored and require a densely planted and well-decorated tank with a sandy substrate. Believe it or not, there are many different brackish plants from which to choose to keep your puffer entertained and comfortable in a natural setting.
Luckily, some of the easiest plants in the hobby can actually withstand relatively high salt levels and will do fine. A full list of brackish plants can be found here. You can also add plenty of driftwood and rocks to keep your puffer occupied.
If you find your fish is swimming up and down the side of the tank, you should be concerned. This is referred to as “glass-surfing” and indicates that the fish is bored and stressed.
The first thing to check is that your fish is still eating; a stressed puffer that is eating can easily be saved!
Next, check for any signs of disease or other injuries and treat as needed. If your fish is fine otherwise, start introducing new aquarium-safe items into the tank or rearranging current decoration.
You will want to do this slowly so you don’t stress out your fish or disrupt the substrate too much. Providing additional hiding places and the right enrichment should help your fish feel more at home.
Setting up a brackish aquarium can sound intimidating, but it’s actually very similar to starting a freshwater tank.
All you need to get going is a proper refractometer to measure and maintain salt levels in the aquarium and marine salt to mix your own brackish water.
Although many sites list figure 8 puffers as a freshwater puffer species, these fish will do much better in a low-end brackish aquarium with a salinity — the measurement of how much salt is dissolved in the water — of around 1.005-1.008; this can be tricky to stabilize at first.
To give your puffer the best life possible, you need to start with slow acclimation. When buying your fish, make sure you know the salinity of the tank the fish is being held in. Note: if you’re going to a large commercial fish shop, they might be sold as a freshwater puffer.
In this case, you will want to take the next few weeks to slowly raise salinity. You can do this through water changes by gradually removing freshwater and replacing it with saltier water until the whole tank is uniform.
Remember, it’s better to take this process slow than fast, though these fish probably easily move through varying salinities in the wild.
Otherwise, figure 8 pufferfish can be a little more sensitive to water parameters than other species.
They need 0 ppm ammonia, 0 ppm nitrite, and minimal nitrates. Figure 8s also need a slightly higher pH than most other freshwater species, preferring the 7.0-8.0 range.
As a tropical species, they need a water temperature that consistently stays between 72 to 82 degrees Fahrenheit (22.2-27.8 degrees Celsius).
Figure 8 puffer tank mates
Like all puffers, figure 8’s are very aggressive fish, so the easiest way to keep them is in a single-species setup with a single specimen. This prevents any possible trouble with tank mates being nipped at, damaged, or even eaten whole.
If you do want to keep your figure 8 puffer with other fish then there are a few options, though you might need to act quickly if things start to go wrong. Remember that these are predatory puffers that can easily chase down slower, smaller fish.
In large enough aquariums, figure 8 puffers can sometimes be kept in groups. These puffers will usually create a pecking order where one becomes dominant over all the rest. Only experts should attempt this, though, as the tank needs very special consideration.
You might find figure 8 puffers can successfully be kept with the bumblebee goby (Brachygobius sp.) as well as other quick, short-finned fish that can tolerate a similar salt grade and temperature. Hobbyists seem to have the most success with molly species (Poecilia spp.).
Figure 8 puffer diet
Diet is one of the most challenging aspects of keeping any puffer and this is no different for our figure 8 friends.
Pellet and flake foods are not suitable (nor will they be accepted by most puffers). Almost all puffers have a nutcracker-like beak that is adapted to chew through hard and crunchy foods.
These beaks will continuously grow throughout their lives and need to be filed down with natural foods. This means that if you don’t offer enough of these hard foods, your puffer’s teeth will eventually overgrow, rendering it unable to eat. Then, you’ll have to clip them by hand.
To keep puffer teeth short, their diet should consist mostly of crustaceans, possibly supplemented with other live or frozen foods, like mosquito larvae and bloodworms.
Live foods are a great option but can become costly over time and it’s recommended to have a separate system for cultivating your own. In this way, you can breed snails, dwarf shrimp, and dwarf crayfish. You can also use store-bought frozen mussels, crab legs, clams, or shrimp soaked in a vitamin supplement.
Juvenile puffers can be fed daily while adult fish only need a meal every few days. Figure 8 puffers are very messy and noisy eaters that are fun to watch! Once they get a snail shell in their mouth, all you’ll hear is them loudly crunching away, only to spit out the shell once they’re finished.
Note: Malaysian trumpet snails are not a suitable puffer food as their shells are too hard and can cause tooth damage.
Figure 8 puffer behavior
So why keep figure 8 puffers if they’re such a challenge?
Their behavior more than makes up for it. These are some of the most intelligent fish species to be found in the aquarium hobby.
Figure 8s always seem to be observing their environment, know when it’s feeding time, and can even learn to differentiate between their owner and other people after a while.
The figure 8 pufferfish can also puff up to two or three times their original size by inflating their stomach with air or water. Puffers typically do this when threatened, although they’ve been seen puffing up in home aquariums for seemingly no reason as well; still, this behavior should not be encouraged.
Are figure 8 puffers poisonous?
Yes, pufferfish are poisonous but only when consumed.
There is some belief that home aquarium pufferfish are not poisonous because they don’t have access to the natural foods that introduce the toxins into their systems. However, this should never be assumed and you should never eat your fish in the first place!
The skin of figure 8 puffers contains the neurotoxin Tetrodotoxin and can be deadly when ingested.
Breeding figure 8 puffer
There have been no reports of figure 8 puffers being bred in captivity so far. However, it is believed that the female may lay eggs along flat surfaces or the substrate, and then the male watches over for a week or so.
Buying figure 8 puffer
Since captive-bred figure 8 puffers are not readily available, be aware that any fish you purchase is likely wild-caught; be sure to quarantine your new pet since wild populations may carry internal parasites or other illnesses.
This means you’ll especially want to make sure that the individual specimen you’re getting can adapt well to aquarium life.
What should you look for in a figure 8 pufferfish?
It’s most important for you to check for signs of disease or illness in the store. The fish should have vibrant colors and look comfortable in its tank with normal behavior.
A good way to check if the fish is comfortable in its tank is by asking the store to feed the fish. This will not only demonstrate that the puffer is willing to eat in an aquarium setting but also that the fish isn’t too stressed out to eat, which could later lead to health problems.
Common figure 8 puffer diseases
Figure 8 puffers are susceptible to all common aquarium parasites, illnesses, and other diseases. However, some illnesses can be hard to treat since puffers don’t readily take medicated food. Some hobbyists try to mix the food with a touch of garlic to entice the fish while others put the medicated food on a piece of thread to replicate the movement of live food.
Luckily, most common diseases and illnesses can be treated with conventional aquarium remedies.
The figure 8 is a popular species of pufferfish due to its exciting personality and limited tank space needs.
However, these fish have a lot of misinformation around them, and it takes some research to understand their brackish habitat needs and live food dietary requirements.
If you have any more questions about keeping figure 8 puffers (Tetraodon biocellatus), or if you want to share your own experiences with this interesting and intelligent fish species, don’t hesitate to leave a comment below!