Introduction
The travancoricus is a species of freshwater pufferfish, from the Carinotetraodon genus, which is endemic to Kerala (was Travancore), Southwestern India.
They are famous for their maximum known size of approximately 25mm (0.98 inches), making it the smallest known species of pufferfish in the world.
Their small size has earned this species several common names which include Pea Puffer, Pygmy Puffer, and Dwarf Puffer. For this care sheet, we are going to refer to them using their most frequently used common name, the Pea Puffer.
Despite this species being the most common pufferfish in captivity, the internet is still plagued with erroneous information. Unfortunately, the more common a species is in captivity, the more folklore seems to surround their husbandry.
Most care guides still completely fail to recognise that this species is in fact a shoaling fish and many recommend unsuitable foods and tanks which are too small.
Pufferfish Enthusiasts Worldwide intends to set the record on this species straight.
In the wild
Pea Puffers are known to inhabit at least 13 different rivers across Kerala and southern Karnataka, in the Western Ghats of Peninsular India.
Unlike most other species of freshwater pufferfish, with a couple of exceptions, Pea Puffers are naturally found in large shoals of their own kind, for social and security reasons. We discuss this in greater detail further in this guide.
The beds of the rivers and streams which these fish call home are covered with leaf litter from the overhanging vegetation and this provides the perfect habitat for the copepods, water fleas, insects and their larvae which these pufferfish prey upon, as they patrol the bottom of these habitats in swarms of their own kind. The presence of sand and detritus within the stomachs of wild-caught Pea Puffers, in a study conducted by the University of Kerala (Laboratory of Conservation Biology, Department of Zoology) indicates that this species is a frequent bottom feeder.
Pea Puffers are classified as ‘vulnerable’ on the IUCN Red List due to habitat loss, pollution, and over-fishing to supply the aquarium trade. They remain relatively common in some areas of India, but are becoming increasingly rarer in other areas where it is believed that the population has decreased by as much as 50% in recent years.
In the aquarium
Pea Puffers are by far the most commonly kept species of pufferfish, owing largely to their average full-grown size of just 2.5cm (0.98 inches). Pea Puffers are very popular and the demand for them has only continued to grow. Imports of wild-caught pea puffers are very common, but they are frequently bred in both home aquariums and commercial breeding facilities across the world, which is reassuring considering that their wild numbers are in decline.
Pea Puffers best thrive in heavily planted aquariums that offer the fish plenty of areas to hide, with lots of visual barriers to break up large and open spaces. Pea Puffers are prey animals and they do not enjoy feeling too exposed. A dense and busy scape helps this species feel safe and secure, knowing that they can take cover quickly if they need to.
More on this below.
A huge variety of different aquascaping styles can be used in a tank for Pea Puffers, with almost endless possibilities. Driftwood, red-moor, mopani wood, rounded boulders, Dragon Stone and Lava Rock are just a few examples of hardscape materials that can be used in your Pea Puffer aquarium.
Java Ferns offer lots of bushy coverage and can be attached to your hardscape, along with other epiphytes, at various heights within the aquarium to break up open spaces. Back ground plants such as Amazon Swords and stem plants, such as Limnophila sessiliflora, can be used to fill the rear of the aquarium and provide the fish with areas of dense overhead coverage, as well as concealing equipment such as heaters and filters from view.
Pea puffers cherish various different types of mosses, such as Java Moss (Taxiphyllum barbieri), Weeping Moss (Vesicularia ferriei), Christmas Moss (Vesicularia montagnei), and will hide and sleep in the soft vegetation. An abundance of moss is actually the secret to breeding the Pea Puffer as they use it as a spawning medium.
For the most part, Pea Puffers naturally inhabit relatively shallow, slow-moving waters, harbored by floating duckweeds and thick vegetation which conceals large groups of them from overhead threats. Floating plants, such as Amazon Frogbit and Water Lettuce, can be used in their tank to recreate their natural environments and provide areas of dappled shade and additional hiding areas.
Pea Puffers are reclusive, shade and shelter-loving creatures because they are prey animals. They're not just eaten by other bigger fish, they're also preyed upon by many piscivorous birds such as Herons, Kingfishers, and Cormorants. Your group of Pea Puffers will feel much more comfortable and secure with a provision of dense vegetation and floating plants in your aquarium, which will encourage them to be more active in all areas of the tank.
The flow in the aquarium should be slow to medium and never overpowering.
Pea Puffers are not strong swimmers, so a powerful current is not suitable.
Pea Puffers are very adaptable fish, but they are intolerant of poor water conditions.
We recommend a minimum water change schedule of 50% every seven days.
Not many people realise how long these little fish can live with the proper care, with the general consensus being that they live for around 3 years. In actual fact, is not unusual for Pea Puffers under good captive management to live for over 6 years, with some known to live to the grand old age of 12 years old.
Substrate
Little known fact, Pea Puffers (like other members of Carinotetraodon) can bury themselves in the substrate when they are scared. They can nose-dive the bottom of the aquarium when they feel that they are at risk of predation and disappear into the substrate like a bullet. We have seen many Pea Puffers become injured when they attempt to do this on substrates that are too hard.
Some Pea Puffers may never be observed to do this, whereas others may exhibit this behavior rather frequently. This is why the substrate should be fine, soft sand regardless, to avoid injury to the fish. Aquasoils and plant substrates can be used, but must be capped with at least 1.5cm of fine sand.
Group size & shoaling
The Pea Puffer, unlike most other species of freshwater pufferfish (with only a couple of exceptions), is a very social species and is naturally found within large shoals. With Pea Puffers, the common idiom of "the more the merrier" couldn't be any more applicable.
It may be easy to think of Pea Puffers, which have been dubbed on social media as 'Murder Beans', as unassailable little predators with no fear of other fish, but this is actually far from the truth, as we have already discussed. The small size of Pea Puffers makes them very vulnerable to predation, and there are many animals (not just other fish) who consider Pea Puffers 'fun-sized' snacks. Contrary to popular belief, the toxin that Pea Puffers contain does not grant them immunity from all predators.
Being a part of a large group gives them enhanced predator detection, with more eyes looking around, which reduces their chances of individual capture and makes it difficult for a predator to target individual fish.
Subsequently, shoaling brings with it a sense of security, which results in calmer and less stressed Pea Puffers.
Shoaling has contributed to the survival of this entire species and these instincts do not disappear when the fish are in captivity. Extensive observations of Pea Puffers (of both wild and captive origin) have revealed that they are more confident, have a better feeding response, live longer, are more expressive with their keepers, and are less aggressive towards conspecifics when they are kept in groups comprising of at least 6. This is especially true when the recommended male-to-female ratio (below) is followed. This is firmly backed up by scientific research, with most studies indicating that shoaling fish express heightened levels of stress when the numbers of individuals are low.
Researchers have found that social fish are less stressed, and therefore calmer, than solo fish. Studies show that communal fish have lower metabolic rates than loners, which means that they have more energy and stamina. Researchers have also found that fish living in larger groups have higher growth rates and their bodies are in better general condition than isolated fish. This makes sense because there is extra energy for the fish to better spend on healing and development.
Groups of 6 are usually the minimum in which a harmonious and balanced group dynamic can be achieved, and this is why smaller groups (containing less than 6) typically experience more infighting. Pea Puffers feel less secure in lower numbers because this causes stress and nervousness that can then contribute to aggressive tenancies.
Dominant members are a healthy part of a group dynamic, but dominance assertion can become problematic when there are not enough members of the shoal for any aggression to be widely distributed across. When a dominant member has only two or three other conspecifics in the aquarium then they may concentrate all of their aggression onto one or two particular fish, which can be catastrophic for the individuals on the receiving end of it. This same behaviour can also be observed in other species of shoaling fish that are housed incorrectly. Additionally, lower numbers also mean that dominant members have less competition in the hierarchy, which often results in those dominant individuals becoming increasingly more and more aggressive. Small groups may work initially, but it is important to consider that behaviour can change over time, especially as the fish go through several different stages of their development.
Through our own extensive observations of captive Pea Puffers, as well as stewarding thousands of members in our groups every year, we are confident in our stance that keeping Pea Puffers in groups of 6 (or more) is the only way to ensure long-term success in captivity.
When Pea Puffers are kept in solitary conditions for too long they begin to express stereotypical behaviors, such as becoming very aggressive. If left for extended periods of time, lone Pea Puffers may never be able to be integrated back into a shoal due to their aggressive tendencies. This shouldn't fuel a debate on whether Pea Puffers can truly thrive on their own, but should instead discourage prospective keepers from keeping single Pea Puffers, because it pushes the fish into a state of significant psychological distress.
The differences between shoaling and schooling
There are two main types of fish crowds, namely schools and shoals. Schools are highly coordinated, tightly packed groups that seem to move like a single organism.
If you are a prospective Pea Puffer keeper, don't expect to observe schooling behaviour. Shoals are looser and less organised gatherings in which individuals swim independently, but in such a way that they stay connected, forming a social group.
The fish understand that there is safety in numbers and hang around together. They become more tightly packed when there's a perceived threat in the area but don't confuse this with schooling. The differences between schooling and shoaling may seem insignificant, but they are crucial for us to recognise in order to understand our fish.
Male to female ratio
Male pea puffers are more aggressive and territorial than females, which is why it is important to have as few males in the shoal as possible. These fish are just as individualist as their larger relatives, so there is no guaranteed ratio, but it is recommended to keep at least two females to every male.
For example, a group of 6 would contain 4 females and 2 males.
Tank size
A group of 6 Pea Puffers should be housed in nothing smaller than a 60L (15.85 US gallons). 60L tanks are common and easy to find throughout Europe but are less common in the United States. USA-based keepers are encouraged to look towards 20-gallon (long) aquariums (approximately 76 liters) as a minimum, but of course, bigger is always better.
Tanks of more length and width are better for Pea Puffers than those with small footprints but more height.
One pea puffer per 10 liters (2.64 US Gallons) of tank water is a good stocking density for this species. This recommendation is based on the fish's behaviour and water quality test results when kept this way.
For example, a 60-liter tank (15.85 US Gallons) can comfortably house the minimum group size of six, long-term.
Further examples:
80L = 8 Pea Puffers
100L = 10 Pea Puffers
120L = 12 Pea Puffers
150L = 15 Pea Puffers
The "5 and then 3 gallon" recommendation
There is an old suggested tank size of 5 US gallons (18.93 litres) for a single pea puffer and then 3 US gallons (11.36 litres) for every additional puffer. This recommendation seems to have been plucked from thin air and is not based on any solid reasoning.
This suggestion also completely ignores the fact that this species is a shoaling species and should never be housed alone.
Water values
Maintain the following water parameters:
PH: 6.5 - 7.5 (in the middle is ideal)
Temperature: 22°C - 27.5°C (71.6°F - 81.5°F)
Nitrate (NO3): below 15ppm (as close to zero as possible)
GH: 5-25 dGH
Tankmates
The pea puffer is almost as famous for nipping the fins of other fish as it is for being small and it is for this reason we strongly recommend a species-only aquarium. However, when Pea Puffers are kept in large shoals (with over 20 members) and large tanks they become much less interactive with other fish because they are so occupied with themselves.
When they are kept in large shoals, they can be housed with some other fish, but this is not completely without risk and the keeper should be prepared to monitor the behaviour and separate the other fish if there is any evidence of fin nipping or harassment.
Any potential tank mate must be peaceful, fast-swimming, short-finned, able to thrive in the same water parameters, and not compete with the Pea Puffers for food. This rules out fish such as Guppies, Angelfish, Gourami, Betta and Barbs. Ideally, any tank mate would be from one of the same regions as the Pea Puffer.
Photo Credit: Stephen Cross The Pea Puffers should not be housed with any bottom-dwelling fish, such as Corydoras, who may encroach on the Pea Puffer's hiding spaces within the scape. Some keepers report a harmonious relationship between their Pea Puffers and small shrimp such as the Red Cherry (Neocaridina davidi) and Amano (Caridina multidentata).
Others report bloodbaths, in which the shrimp are slaughtered.
Providing that the water values are suitable, the smaller species of catfish from the Otocinclus genus may be used in a Pea Puffer tank for minor algae control. Bear in mind that Otocinclus also benefit from being in groups, being found within shoals of thousands in the wild, and because they are obligate aufwuch eaters, the tank needs to be both large enough and mature enough to support a group.
Sexual dimorphism
Juvenile C.travancoricus are very difficult to accurately sex, but become more sexually dimorphic as they age. Mature males have an obvious dark line that runs lengthways over the ventral surface (underside), which the females lack.
Typically, mature males have a pattern of closely arranged lines around the eye, which are frequently referred to as ‘wrinkles’. Sexually mature females are also rounder in the body than males.
Buying your pea puffers
We definitely recommend visiting the store to hand-select the individuals for your shoal, rather than buying them online without seeing the quality of the livestock first.
It is not uncommon for Pea Puffers to be sold in a malnourished state and the inexperienced keeper may struggle to completely recover the puffer's health in good time.
Select Pea Puffers who look bright, active and alert, with no signs of undernourishment or illness. They should obviously be well fed and their bodies should be round and plump.
As we said, this species is classified as 'vulnerable' by the IUCN because their wild numbers are declining. Now, although the aquarium trade is not entirely to blame, with the threats to this fish also coming in the shape of pollution and habitat loss, we should encourage buying only captive-bred examples, so do not be shy to ask your retailer where the livestock has been sourced from and avoid buying wild-caught.
Introducing new members to an existing shoal
It is best to buy every member of your shoal from the same place, at the same time, which will ensure that all of your Pea Puffers settle into the aquarium simultaneously.
If you are introducing new Pea Puffers into an existing group then firstly make sure the new members are of roughly the same size as your other members and rescape the tank before introducing the new members, to break up established territories within the tank.
Treating for parasites
Internal parasites (endoparasites) are the only thing that we recommend treating prophylactically. We recommend treating worms, even if the fish are captive-bred, appear to be healthy, and show no signs of having parasites. We encourage this because endoparasites can sometimes go unnoticed for a very long time and they are capable of causing serious problems.
We recommend a Levamisole HCL based medication, such as eSHa NDX.
Levamisole HCL is effective against Stomach worms, Nodular worms, Hookworms, and Lungworms. It is especially effective against Nematodes (roundworms), such as Capillaria, Eustronggylides, Camallanus, and Contracaecum.
Levamisole HCL is not the medication of choice against Cestodes (tapeworms), and this is where a praziquantel-based medication (such as PraziPro) should be used.
Some small crustaceans can act as intermediate hosts for some parasites, so depending on what you feed to the pufferfish and where you source the food from, you may have to worm the fish on a regular basis.
We have more information on how to correctly worm your pufferfish under the 'Guides' tab in our Facebook groups, Pea Puffer Enthusiasts Worldwide and Pufferfish Enthusiasts Worldwide.
Antibiotic based medications
Antibiotic-based medications should not be used for worming any fish unless specifically prescribed by a veterinary professional. This includes common medications with active ingredients like Metronizadole, Kanamycin, and Erythromycin.
The use of antibiotics without a veterinary prescription is illegal in some countries.
Antibiotics do not discriminate between 'good & bad bacteria and can damage the fish's gut microbiota. The gut microbiota are the microorganisms (including but not limited to bacteria, archaea, and microscopic eukaryotes) that live in the digestive tracts of animals. Their gut flora play an essential role in the fish’s development, digestion, nutrition, immunity and disease resistance. Damaging this gut flora can have many negative implications and it can take a long time for the microbiota to fully recover after antibiotics have been used. Changing the levels of gut microbiota can disturb what is a finely balanced ratio of “good” and “bad” bacteria. By removing some of the “good” bacteria, you can actually encourage the growth of “bad” (pathogenic) bacteria, predisposing your fish to further illness. The most noticeable symptom of damaged gut flora is a reduction in appetite, owed to uncomfortable digestion. This can be especially troublesome for fish that have been freshly imported and need to build up their energy reserves.
The use of antibiotics in the aquarium can also damage the microorganisms which maintain the nitrogen cycle in the tank, potentially exposing your fish to toxic levels of ammonia and/or nitrite.
Another very serious effect of antibiotic use is the increase of antibiotic-resistant bacteria found after their use, which can invade the host (your fish) and cause illnesses that are very difficult to treat.
The use of antibiotics can make infections that are very easy to treat now, very difficult (sometimes impossible) to treat in the future. We are now seeing antibiotic-resistant strains of Aeromonas, Pseudomonas, Columnaris, and other bacteria invade home aquariums, after either they or the store from which the fish were purchased, used antibiotics.
Notable behaviour
They have been known to jump out of the water when being pursued by one another, so they must only be housed in an aquarium with a tight-fitting lid.
They are very intelligent and will beg their owners for food once they have made the association.
The Pea Puffers may occasionally circle other Pea Puffers with their tail curved. This is a normal sign of defense and short-lived spats are quite common. This behaviour can also be observed when the fish is investigating an unfamiliar object.
Feeding
Pufferfish Enthusiasts Worldwide will always encourage keepers to replicate the natural diet of their pufferfish as closely as possible. Wild pea puffers eat a very diverse range of prey and it is your responsibility as the keeper to provide as many different kinds of appropriate foods as possible.
Aside from providing a variety of flavours and textures for food enrichment, a varied diet of suitable foods will supply a greater spectrum of nutrients to your fish that are essential to the health, growth, development, and long lifespan of your pea puffers.
The following diet suggestions and food items are suitable for pea puffers of all ages and sizes, but portion and food item size must be modulated to suit the size of the fish.
The Pea Puffers will rarely take to flake food or pellets or show any interest in freeze-dried foods and because of this, it is important to ensure that the Pea Puffers receive a varied diet of the correct foods.
Live and frozen foods are usually excitedly devoured.
Our preferred foods for these fish include:
Pinhead crickets
Aphids
Glassworm (phantom midge larvae)
Grindal worm
Daphnia/water flea (live or frozen)
Brineshrimp/artemia (live or frozen)
Small snails - read below
Small earthworm (wisps)
Blackworm
Whiteworm
Copepod
Mini bloodworm (live or frozen)
This species should not be offered krill, cockle, mussel, clams, oysters or similar mollusks.
Not any one food should make up more than 20% of the fishes overall diet, with bloodworms (read below) not exceeding 10%.
It is best to alternate between different foods on a daily basis and feed several small meals throughout the day rather than offering larger, less frequent meals. This helps with ensuring that the fish are receiving a varied diet, but also to keep the pufferfish occupied.
Feeding snails and hard-shelled foods
Pea puffers will eat small snails, such as young Segmentina nitida (ramshorn snails) and Physella acuta (Bladder snail), but they do not need to be fed these snails on a very regular basis.
The beak of this species does not grow as rapidly as some others, so the need to feed hard-shelled foods is reduced.
The rotting bodies of dead snails can cause significant ammonia spikes in the aquarium, so it is important that uneaten snails are removed from the aquarium.
Filtration and tank maintenance
This pufferfish is intolerant of poor water conditions, so a high level of biological and mechanical filtration is needed to deal with the amount of waste that this fish produces.
Good filtration combined with excellent husbandry is essential to the health of this species.
Frequent water changes must be carried out to maintain NO3 (nitrate) levels below 15ppm; or as close to zero as possible.
We recommend a minimum water change of 50% every seven days and extra attention should be afforded to ensure that the base of the dense scape is free from detritus.
Inflation
Pea Puffers can inflate themselves when frightened or stressed.
They should never be provoked into inflating!
If the fish needs to be moved for whatever reason, it should be herded into a watertight container under the surface of the water to prevent it from inhaling air.