Updated: Jul 18
The travancoricus is a species of freshwater pufferfish, from the Carinotetraodon genus, which is endemic to Kerala (was Travancore), Southwestern India.
It is famous for its maximum known size of less than 25mm (0.98 inches), making it the smallest known pufferfish.
This small size has earned this species several common names including, pea puffer, pygmy puffer or dwarf puffer.
In the wild
The C.travancoricus is known to inhabit 13 different rivers, in addition to several estuaries, across Kerala and southern Karnataka in the Western Ghats of Peninsular India.
The beds of the rivers and streams which these fish inhabit are covered with leaf litter from the overhanging vegetation.
This provides the perfect habitat for the copepods, water fleas, insects and their larvae which these pufferfish prey upon.
The presence of sand and detritus within the stomachs of wild-caught C.travancoricus, 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.
The water chemistry within their distribution ranges is variable and they can be found in both soft, acidic waters and hard, alkaline waters.
Although the C.travancoricus is considered a freshwater species, the water in the Vembanade wetlands where this species can be found is slightly brackish. This only goes to show that the C.travancoricus is very adaptable to a wide range of water conditions.
The C.travancoricus is classified as ‘vulnerable’ on the IUCN Red List due to habitat loss, pollution and over-fishing to supply the aquarium trade.
It remains relatively common in some areas of India but it is becoming increasingly rarer in other areas where it is believed that the population has decreased by as much as 50%.
In the aquarium
Owing to their full-grown size of just 2.5 cm (0.98 inches), the C.travancoricus is a very popular choice for nano aquariums across the world. Imports of wild-caught C.travancoricus are very common and the species is frequently bred in both the home aquarium and commercial breeding facilities.
Unlike most pufferfish - who are primarily solitary creatures - the C.travancoricus is found within large shoals in the wild and should always be kept in groups consisting of at least six individuals.
This species displays signs of stress and anxiety when they are housed alone - as a single specimen - or in groups less than six (read Tankmates and group sizes).
They thrive best in heavily planted tanks with a dense scape, that provides areas to hide and lots of visual barriers. Such a scape offers them a sense of security in knowing that they can take cover if a predator swims close by.
Dragon stone, water-logged wood and rounded boulders
can all be utilised in their scape, alongside plants such as Amazon sword, Java fern, crypts, Anubias, aquatic stem-plants and various mosses.
Although these pufferfish are very adaptable, they are intolerant of poor water conditions so a mature tank, decent filtration and frequent water changes are essential.
One C.travancoricus per 10 litres (2.64 US Gallons) of tank water seems to be a good rule of thumb.
For example, a 60 litre tank (15.85 US Gallons) can comfortably house 6 specimens, long-term, and the tank should always be scaped in the aforementioned fashion. With that said, the recommended minimum tank size is 60L (15.85 US Gallons) for the minimum group size of six; 1 C.travancoricus per 10 litres (2.64 US Gallons) of water.
Maintain the following water parameters:
PH: 6.5 - 7.5 (in the middle is ideal)
N03: below 15ppm (as close to zero as possible)
GH: 5-25 dGH
The C.travancoricus is naturally found within shoals, for social and security reasons.
They should never be kept alone or in group sizes consisting of less than 6 individuals.
When kept in groups of at least six, they are much more confident, have a better feeding response, are more social and less aggressive to each other.
Solitary C.travancoricus are likely to become shy, nervous and emaciated owing to a decreased appetite.
Male to female ratio
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.
Example, a group of six should contain 4 females and 2 males.
The C.travancoricus is almost as famous for nipping the fins of other fish as it is for being small. For this reason, I strongly recommend a species only aquarium. I am reminded of a time when a trio of C.travancoricus jumped over the divider of a barrack holding tank (read ‘Notable behaviour’ for jumping) and attacked a male Siamese fighting fish (Betta splendens) and a group of Harlequin rasbora (Trigonostigma heteromorpha) in the neighboring aquarium.
Providing that the water values are suitable and that the aquarium is both large enough and mature enough to support a group, the smaller species of catfish from the Otocinclus genus may be used in the C.travancoricus tank for minor algae control.
This isn’t without risk and the keeper should monitor the behaviour and be prepared to separate the catfish if the C.travancoricus exhibits any aggression towards them.
Some keepers report a harmonious relationship between their C.travancoricus and small shrimp such as the Red Cherry (Neocaridina davidi) and Amano (Caridina multidentata).
Others report bloodbaths, in which the shrimp are slaughtered.
Juvenile C.travancoricus are very difficult to accurately sex.
Mature males have an obvious dark line which runs length-ways 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 the males.
The common idiom is that "big things come in small packages" and that is definitely true with the C.travancoricus. They are known to be fearless and aggressive and will often bombard much larger fish.
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 C.travancoricus may occasionally circle tank mates with its tail curved. This is a normal sign of defence. This behaviour can also be exhibited when the fish is investigating a new object.
Little known fact, species from the Carinotetraodon genus will bury themselves in the substrate when scared. They 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. This is why the substrate must be fine, soft sand to avoid injury to the fish when they do attempt to do this.
The C.travancoricus will seldom take to flake food or pellets or show any interest in freeze-dried foods. Live and frozen foods are usually excitedly devoured.
My preferred foods for these fish include:
Daphnia/water flea (live or frozen)
Brineshrimp/artemia (live or frozen)
Small snails - read below
Mini bloodworm (live or frozen)
Not anyone food should make up more than 20% of the fishes overall diet, with bloodworms not exceeding 10% owing to their low nutritional value. There have been reports of C.travancoricus choking on normal-sized bloodworms, so I choose to use mini bloodworms to prevent this. To ensure that their nutritional needs are being met, offering a varied diet is a very important consideration in the care of this species.
I alternate between different foods daily, offering the fish as much variety as possible. I also prefer to feed several, small meals per day over one large feeding.
Feeding snails and hard-shelled foods
The C.travancoricus 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.
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. However, these fish do not appreciate a strong flow.
Good filtration combined with excellent husbandry is essential to the health of this species. Frequent water changes must be carried out to maintain N03 (nitrate) levels below 15ppm; or as close to zero as possible. Extra attention should be afforded to ensure that the base of the dense scape is free from detritus.
C.travancoricus 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.
This care sheet is written with the aim of providing the optimal care for this species of fish. Pufferfish Enthusiasts Worldwide endeavours to inspire and promote the highest standards of care - not basic or minimum care - using the best evidence available to us at the time.
Every care guide will always be updated whenever new evidence or previously unknown information comes to light. This page was last updated on 17th July 2020.
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