Colomesus asellus is an active freshwater species from South America, which can attain a reasonable size and requires a good amount of swimming space. Given enough room, this species can usually be housed with fast-moving fish species such as some members of the Danio and Devario genera. However, as with all species of puffer, there will always be exceptions to this rule (such is the diversity of individual puffer personalities) so careful observation of all aquarium occupants is recommended. It must be said that if you are aiming to create a calming aquarium, you should avoid purchasing this extremely lively species, as watching its activities can make you feel quite dizzy! Unfortunately, C. asellus is prone to two major problems. Firstly, they often arrive from the exporters with whitespot, or else develop it when moved to their new home (no matter how carefully they are caught/transported) so have some treatment on-hand just in case, and secondly, their teeth grow alarmingly quickly and therefore must be offered plenty of snails and encouraged to 'bite out' partially opened cockle-in-shell, in order to keep the teeth in check. South American Puffers are not suitable for general community aquaria; indeed slow-moving fancy-finned tankmates will suffer. Conspecific fin-nipping will also occur in cramped aquaria, so ensure your puffers have enough space and territories/visual barriers created amongst bogwood and plants. The aquarium should be well filtered, with high levels of oxygenation and a reasonable current. May also be seen on sale as Amazon Puffer or Colomesus Puffer.
Add food simultaneously at several locations in the aquarium to avoid the Puffers accidentally injuring one another in their enthusiasm to get at the food. Meaty frozen foods such as brineshrimp, Mysis shrimp, mosquito larvae, chopped cockle and mussel meat, chopped shell-on prawns, small snails, partially opened cockle-in-shell etc should be given. Hard-shelled foods MUST be offered on a regular basis to help keep the beak in check. Some aquarists breed small aquatic snails in a separate small aquarium, where they reproduce rapidly and can be easily harvested for feeding times.