Updated: Dec 17, 2020
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 at the time.
The main priority at Pufferfish Enthusiasts Worldwide will always be to provide the most accurate and up to date information pertaining to individual species of pufferfish and their care. Although we do greatly encourage the use of binomial names (scientific names), because common names can be so misleading for pufferfish, we sometimes have to make concessions with the care sheets for SEO reasons. We realise that most people are not going to search "Colomesus asellus care" and are instead more likely to search for "Amazon puffer care", so this care sheet is going to refer to them by their most frequently used common name, so that new and prospective owners will be able to find this information through a Google search.
The asellus is a species of freshwater pufferfish, from the Colomesus genus, which is endemic to tropical South America.
This C.asellus is a very popular aquarium fish and is commonly referred to as the Amazon Puffer, Peruvian Puffer and the South American Puffer (sometimes abbreviated to SAP).
Owing to the convenient size and social nature of this pufferfish, it has become very popular with keepers across the world.
Despite this species being one of the most common pufferfish in captivity, the internet is still plagued with erroneous information and most care guides completely fail to recognise that this species is in fact a shoaling fish, or recommend unsuitable foods which may be very unhealthy for the fish over the long term and tanks that are too small. Unfortunately, the more common a species is, the more folklore seems to surround them. Pufferfish Enthusiasts Worldwide intends to set the record on this species straight.
In the wild
The distribution range of Amazon puffer includes the Tocantins River basin, as well as numerous other rivers in South America.
In the wild, this species eats a variety of insecta, but almost half of their diet is comprised of Ephemeroptera nymphs (known as mayfly, fishflies and shadflies). Gastropoda (snails) make up just over a quarter (25.07%) of an adults natural diet and around 6.5% of a juvenile's diet. They also eat Chironomidae (known as non-biting midges), other insects, gastropods (snails) and plant/algae matter.
In the aquarium
The Amazon puffer is prized for being "friendly" and is commonly referred to as the "community puffer". While it is true that the Amazon puffer is, by far, one of the friendliest species of freshwater pufferfish, they are not perfectly peaceful and we will discuss this further within the section on tank mates in the care sheet (below).
Amazon puffers are intelligent fish who need lots of stimulation and social interaction with their own kind.
You can give an enriching aquarium by providing an elaborate scape with lots of caves and hiding spaces to explore, but keep in mind that they are very active swimmers so they should always have plenty of open swimming space too.
We recommend heavily scaping the back of the tank with plants and hardscape materials, while leaving open swimming space at the front, which will encourage the fish to swim the length of the aquarium where you can watch them. A heavily decorated tank will help the shy, yet active Amazon puffer feel secure and contained, knowing that they can take cover quickly if they need to, which will result in more natural foraging and explorative behaviours.
Amazon puffers appreciate highly oxygenated water with a medium to strong flow, which they enjoy swimming against. The strength of the flow in the aquarium is usually achieved with spray bars from canister filters, angled towards the top of the water. Keeping a slightly dropped water level so that the returning water from the filter splashes down onto the surface creating agitation and facilitating a gas exchange for high levels of oxygenation.
Powerheads with narrow gaps in the grill may be used to create additional flow. We would advise that cages or guards (such as anemone guards) are used on powerheads to prevent injury to the fish if they become trapped.
Breeding this species in captivity is unfortunately very labour and resource-intensive, which would make captive-bred examples very expensive compared to wild-caught specimens.
Therefore, any commercial breeding attempt would likely be economically unviable.
Although the Amazon puffer is not a wallowing species, we do always recommend that a fine sand substrate is used with this fish. Apart from resting on the substrate at night, the Amazon puffer doesn't interact with the ground much, but a fine sand substrate is soft and will prevent injuries such as scrapes. Fine sand is also much cleaner than conventional gravel substrates, because it doesn't allow uneaten food and other organic matter to fall between the gaps, which will help you keep the aquarium very clean and maintain good water quality.
Group size is very important for this species of puffer. Unlike most other species of freshwater pufferfish, with a couple of exceptions (such as the Pea Puffer), the Amazon puffer is naturally found within shoals, for social and security reasons.
Being a part of a large group gives them better foraging success and enhanced predator detection, with more eyes looking around. Subsequently, shoaling brings with it a sense of security and is why this species becomes very stressed, nervous and shy when kept either alone, or in groups that are too small.
The Amazon puffer should always be kept in groups consisting of at least six individuals.
When kept in groups of at least six, they are much more confident, relaxed, have a better appetite/feeding response and enjoy a longer and more fulfilling life.
The "single or group of six" recommendation
The "single or group of six" recommendation works well for some other species of puffer, such as the Tetraodon schoutedeni, but it is totally unsuitable for the Amazon puffer. Recommending this for the Amazon puffer completely fails to recognise that this species is highly social and neglects to mention that these fish display signs of severe stress and anxiety when they are housed alone. Solitary Amazon puffers become very erratic and their behaviour in these circumstances is described as ‘neurotic’.
Our recommended tank size is at least 200 litres (52.83 US gallons) long for the minimum group of six, with additional space for further stocking.
Amazon puffers are very active swimmers and they will spend much of their time travelling the length and breadth of the aquarium. For this reason, they should be housed in a tank that is at least 100cm (39.37 inches) in length.
Maintain the following water parameters:
PH: 6.0 - 7.5
N03: below 15ppm (as close to zero as possible)
GH: 4-15 dGH
Although the Amazon puffer is considered to be one of the most 'peaceful' pufferfish species by many in the trade and hobby, it is not suitable for the typical community aquarium, despite advice to the contrary on some areas of the internet.
Research into their natural diet has shown that the stomach content of wild-caught individuals include small amounts of fins and scales from other fish and anecdotes from keepers often include caveats of this species nipping the fins of some other fish if given the opportunity.
Other fish can be kept alongside this species of pufferfish, but allospecifics (members of a different species) must be very carefully considered. Any potential tankmate must be non-aggressive, fast-swimming, short-finned and able to thrive in the same water values. This rules out fish like guppies, angelfish, gourami and Betta.
Providing that the water values are suitable and that the aquarium is mature enough to support a group, species of catfish from the Otocinclus genus may be used in the Amazon puffer tank for minor algae control.
Also, dependant on water values and tank size, Amazon puffers can be housed with groups of Hemigrammus rhodostomus (Rummy-nose tetra), Paracheirodon axelrodi (Cardinal tetra) and other similar Amazonian fish.
Buying your Amazon 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 Amazon 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 Amazon puffers who look bright, active and alert, with no signs of malnourishment or illness. They should obviously be well fed and their bodies should be round and plump.
Treating for parasites
Internal parasites (endoparasites) are the only thing that we recommend treating for prophylactically. We recommend treating for worms, even if the pufferfish appear to be healthy, or showing 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 HCI based medication, such as eSHa NDX. Levamisole HCI 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 HCI is not the medication of choice for 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 a guide for parasites coming soon, which we will publish and leave a link for here when it is completed.
They are very intelligent and will beg their owners once they have made the association between humans and food.
As this species is a very active swimmer, they can be observed frequently swimming the length of their aquarium. However, if these fish are stressed, their swimming by be erratic. This behaviour is commonly referred to as "glass surfing".
There is no known method of determining the sex of this species for the home aquarist.
One of the most important elements in keeping the Amazon puffers is providing a varied and balanced diet, in order to ensure that their nutritional needs are being met.
When housed correctly, this species typically has a very good appetite and is therefore much more forgiving and less picky than other species, even accepting pellet and other prepared foods.
Our preferred foods for these fish include:
Small snails - read below
Small earthworm (wisps)
Glassworm (phantom midge larvae)
Quality pellet food (such as JBL NovoGranoColor, JBL GranaDiscus, JBL GranaCichlid)
Repashy - Grub PieFish
Repashy - Soilent Green
Fluval® Bug Bites™
This species should not be offered krill, cockles, mussels, clams, oysters or similar mollusks.
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 hard-foods and teeth maintenance
Amazon puffers have very fast growing teeth, so it is absolutely essential that the keeper of this species offers hard-foods on a daily basis.
Feeding hard foods, such as the pellets mentioned above, and employing the methods under 'Tips to help' (below) are the easiest and most practical ways of ensuring that the fish's teeth remain at a healthy length.
Failure to provide hard-foods regularly will quickly result in serious dentistry complications that will require intervention by either the competent aquarist or a veterinary professional.
If you intend on keeping this species then you may be told that you will have to familiarise yourself with the process of trimming their teeth. The truth is that overgrown teeth are very easily avoided by feeding the correct type of foods and removing the need of having to intervene in the first place should be the priority. Simply put, if the keeper is having to have the fish's teeth trimmed periodically then their puffer's diet needs revising.
It is recommended that keepers of this pufferfish breed aquatic snails in a separate system so they can offer snails as a part of a varied diet. Maintaining a high mineral content (using buffers if necessary) in the water of the snail breeder can help the keeper in developing shells of the desired hardness.
Amazon puffers certainly prefers some species of snails over others.
The shells of Melanoides tuberculata and other trumpet snails are too hard for Amazon puffers and may cause them to associate snails with pain/difficulty if they injure themselves trying to eat them. The aforementioned species also lack substantial amounts of meat. The best snails are Physella acuta (bladder snail), the various species commonly referred to as ‘ramshorn snails’ and small/young terrestrial snails which are cultured for reptile and human consumption.
Snails alone will not maintain their teeth
Although snails are very nutritious, they shouldn't be relied upon solely for teeth maintenance because culturing enough snails to maintain the teeth - of at least six Amazon puffers - can be very challenging, so the hard-pellets are the perfect substitute.
Tips to help
In addition to feeding hard pellet foods, the keeper can also utilise the highly nutritious foods from Repashy by smearing the mixture onto rocks, or pieces of cuttlefish bone, and then submerging those rocks into the aquarium. The pufferfish will 'scrape' the Repashy from these objects, helping to wear their teeth.
Amazon puffers are believed to do this in the wild, scraping algae from stones and rocks in their natural habitat. We have included Repashy Soilent Green in the list of preferred foods because it is essential that they receive plant matter from their diet.
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 N03 (nitrate) levels below 15ppm, or as close to zero as possible. We recommend a minimum water change schedule of 50% every seven days.
Amazon 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.
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