Many people choose an aquarium as an allergen-free, quiet and low-maintenance alternative to other types of pets. In general however, your interaction with the fish is limited to watching them swim around and eat. Fish will even learn to anticipate feeding time and dart about at the surface when you approach with a pinch of flakes – although some might argue that this can hardly be compared to playing fetch with a golden retriever.

There are, however, a few species of aquarium fish that have – dare we say it – a personality of their own. These are generally predatory fish, willing to work a bit for their food, and with a little more intelligence than you average neon tetra. They aren’t necessarily the prettiest fish, or well-suited to a community aquarium, but if you’re looking for a ‘hairless puppy’, they just might do the trick.

Oscars

Oscars Cichlids are an intelligent, carnivorous species originating in the slow-moving rivers of the Amazon basin in South America. They are an oval-shaped fish with distinctive, pouting lips. They come in various mottled or marbled combinations of black, red, orange and albino, and their small scales give them a velvety appearance. A healthy Oscar might live up to sixteen years.

They are lively, playful fish, especially when feeding, and are known to splash at the surface and rearrange the decorations – even spitting them right out of the tank. Live plants may need to be potted and securely anchored or they will frequently be dug up. Plastic ornaments may become toys, and many Oscar owners find that rotating the ornaments every so often gives the Oscar a chance to explore (and alter) a new environment.

Oscars enjoy a variety of frozen, dry, and live meaty foods. They are voracious eaters and will quickly identify the hand that feeds. They can be trained to roll over for food, and some will even learn to enjoy being petted. They are very attentive, sometimes demanding, and occasionally spoiled. They grow quite quickly—and up to a foot in length. A 30-gallon tank may be sufficient for a juvenile, but an adult might need 75 to 100 gallons. Although not overtly aggressive, they usually make poor mixed-species community fish due to their predatory nature. Suitable tank-mates might include fish that are too large to become prey. Although individuals are difficult to sex, they will pair off if housed in a small group. Once paired, they are easy to breed and make devoted parents, even to the point of chewing up food for their young.

Pacus

The Pacu is a relative of the Piranha and greatly resembles it; however, it is mainly herbivorous and uses its powerful mouth to crush seeds and nuts in the wild. They are opportunists however, and will eat most things that fit into their mouth, including smaller tank-mates, given the chance.

In an aquarium, Pacus can be fed on a variety of flakes, pellets, and green leafy vegetables. Over the course of several years, they can grow quite large – up to two feet long – and as such they must be kept in extremely large tanks (up to 250 gallons when full-grown). Pacus may live for decades in captivity.

Pacus are known to recognize their owners and enjoy petting. They will frequently beg for food and eat right out of your hands. Their personality has been described as very similar to that of a dog. They can be kept with other Pacus or large fish, and are very playful, often chasing each other around the tank. Their rambunctious nature, however, means that they may inadvertently crash into and damage ornaments or other obstacles in the tank. Heaters are a particular hazard, as a damaged heater can electrocute the fish (and the owner). Pacus should only be kept with sturdy decorations, filters, and heaters.

Although Pacus originate in South and Central America, they have been introduced to many freshwater areas in part due to aquarists’ tendency to “free” them as they get bigger, and sometimes out-compete or displace native species, and it is illegal to release them into the wild. A Pacu which has outgrown its welcome can instead be sold to a friend, a tropical fish dealer, or better yet, donated to a local zoological aquarium.

Pufferfish

Pufferfish are also known as Blowfish or Fugu, and are well-recognized for their unique defense mechanisms. When threatened, they will gulp large amounts of water or air and swell to two or three times their original size, startling potential predators and becoming quite ungainly prey. Some puffers are also spiny (such as Porcupine pufferfish). In addition, wild pufferfish carry a toxin which is quite deadly when eaten. Most captive puffers do not carry this toxin because they must ingest certain bacteria found in the wild in order to produce it.

Pufferfish come from a variety of environments all over the world, and there are brackish, marine, and a few distinct freshwater species. Many species that originate in an estuary environment will navigate closer to the ocean as they grow, and as a result, they may require saltier water as they age. Due to their various and contradictory requirements, you should be certain of species identification before purchasing an individual.

Besides their ability to inflate, all puffers carry the distinct feature of four teeth forming a sort of beak, which they use for crushing the shells of their prey, often shrimp, crabs, mussels or snails. Puffers will eat almost anything meaty but should be given enough crunchy food to wear down their teeth, or they may overgrow and require a trimming.

Pufferfish are a playful and mischievous species and very attentive to their owners. They will beg for food and eat until their bellies are so round they can hardly maneuver about the tank (although care should be taken not to overfeed). They mainly use their pectoral fins for swimming, and it gives them a peculiar darting-and-hovering movement in the water, which has been compared to hummingbirds. Their bulging eyes move independently, and combined with their tiny beaked mouths, the effect is a goofy and surprisingly expressive face.

Although temperament varies somewhat by species, many puffers are aggressive fin-nippers and should be kept only with larger or faster fish. In general they are more docile with other species than with other puffers, and some may do very well in a community tank, although they are said to become more aggressive as they grow.

Other Personable Fish

In a small aquarium, a male Betta can be an attractive and interactive fish. Angelfish are also curious and responsive. Among cichlids, there are a variety of personalities available and a tank with several species can be demonstrate a dizzying array of social interactions and hierarchies. Many larger predatory species, such as the Arowana, are said to recognize their owners and act accordingly. Even if you are restricted to aquarium-dwelling pets by allergies or lifestyle, you can still live with a creature that recognizes, responds to, and appreciates you.

By Jenn Perret – Pets.ca writer