This week’s fish of the week is an oddball species that has become more and more popular in recent years, in no doubt due to its great character and suitability for a ‘standard’ home aquarium. It’s the Colomesus asellus more commonly known as the South American Pufferfish or Amazon Pufferfish, first described by the German zoologists Johannes Peter Muller & Franz Hermann Troschel in 1849.
The scientific name for this order of pufferfish is Tetraodontidae, from the Greek words tetra meaning ‘four’ and odous meaning ‘tooth’. This group of freshwater pufferfish have four fused ‘teeth’ that form a kind of beak (actually a modification of the jawbone).
South American puffers have been known to reach 13cm although 7-8cm is more typical, they are green in colour with white bellies and patterned with black transverse bands across the dorsal surface, they can be distinguished from other members of the colomesus genus by the presence of a unique transverse row of dermal flaps across the chin which is absent in other members of the genus.
South American puffers are natively found throughout much of the Amazon basin in Brazil, Columbia, Peru and Ecuador although they tend to thrive in highly oxygenated, cooler conditions (20-26°C, pH 5.5-8.0, KH 2-15°H) which should be replicated as closely as possible in the home aquarium.
Although not a large fish, the fact they like to be kept in groups (unusual for puffers) means that a 100-litre aquarium would be the minimum required, these puffers are very sensitive to poor water quality and, as previously mentioned, prefer highly oxygenated water, for this reason good external filtration would be recommended along with the use of air stones or power heads to increase the dissolved oxygen levels. Decoration of the aquarium should try to replicate the conditions found in the Amazon so sand or fine gravel with plenty of plants both rooted and floating along with bogwood or azalea roots to replicate fallen and overhanging branches.
South American puffers are not usually fussy feeders and readily accept most frozen or live foods found in your local aquatic retailer, they do have one notably requirement; however, the beaks of these puffers continue to grow throughout their lives and can become overgrown making feeding difficult. To prevent this, they should be regularly offered meals of shelled invertebrates such as snails, crab legs, cockles etc.
The face-paced attitude and inquisitiveness of these puffers makes them unsuitable for the general community aquarium, however as previously mentioned, they do prefer to be kept in groups with 6 being the minimum required to prevent aggression.
Being puffers, these fish do have a couple of special characteristics odd note, firstly is their ability to inflate of puff up, they are able to do this as they lack traditional scales and instead have a tough but flexible skin covered in tiny spines. This allows them to inflate themselves by drawing either water or air into a specialised ventral diverticulum of the stomach, hopefully making them too large to be eaten by whatever is threatening them. Secondly pufferfish are poisonous (not venomous) which means their flesh and skin contains a toxin, in this case saxitoxin and tetradotoxin, which are both toxic to humans so always use a net and ensure you thoroughly wash your hands if you come into direct contact with these fish.
With their abundance of character and inquisitiveness, these puffers really do warrant a species aquarium and easily qualify as this weeks Fish of the Week.