By: David Ogando Jr.
For most people, when they choose to get a fish from the store, they tend to look for the vibrant and modern kinds such as the clownfish or the tangs or the cichlids of Africa and Central & South America. However, there are also some examples of fascinating fish that are living fossils from the past. They’ve outlived the dinosaurs and can become a wonderful addition to your tank! Below are some examples of “primitive fish” that you may find at Absolutely Fish.
Bichirs (Polypterus spp.)
Native to Africa, bichirs (also known as a polypterus in the aquarium trade) naturally live in poorly oxygenated waters, and are also obligate air breathers similar to some species of lungfish. Unique to bichirs is the ability to exhale spent air from their lungs using their dorsally placed spiracles. Some can grow to a maximum length of ~2.5 feet and require a tank size of at least 90 gallons, while others remain smaller at a maximum size of ~12 inches. They are a predatory fish that will eat anything that can fit in their mouth (Yang). It is best to feed bichirs a varied diet of dry and frozen foods such as shrimp, bloodworms, and nightcrawlers that can reach the bottom of the tank where they reside. However, they are otherwise a peaceful, hardy, and active addition to one’s sandy, planted tank and can be placed with other larger fish such as silver dollars, clown loaches, and larger community fish.
Gars are native to North and Central America, and are known by their elongated body and snout. They also possess entirely ossified skeletons! Similar to bichirs in how big they may get along with possessing primitive ganoid scales, gars require a large tank size to grow of at least 90 gallons. They will also eat anything that they can fit in their mouth. These fish also require a meaty diet and though can be fed feeder fish such as minnows and shrimp, they can also be weaned from a young age to accept frozen and pellet-based food (Tokic). Because of their diet, gars emit a heavy bioload, thus require a strong filtration system with frequent water changes. Gars are hardy fish, native to backwater areas of lakes & rivers, occasionally breathe atmospheric air using a highly vascularized gas bladder as a lung. These primitive fish will pair well with other larger fish they will not perceive as prey such as bichirs and Geophagus (Tokic.)
South American Lungfish (Lepidosiren paradoxa)
While lungfish have formerly been abundant worldwide in places such as Africa, Australia, and South America, L. paradoxa is the sole species found in South America, specifically throughout the Amazon, Rio Paraguay, and other slow-moving waters. This species can grow to a maximum of approximately 4 feet, but a 90-gallon tank is satisfactory for captive-raised specimens due to them being slow-growing. They require space for them to breathe, a result of them possessing a physostomous swim bladder which acts as a primitive lung. Lungfish will receive the best nutrition from meat-based pellets and flake food. Predatory in behavior, it is best for them to be housed alone because while they will not attack fish that they do not view as a threat, they are at risk of being injured by other fish due to their slower movement (a consequence of possessing cosmoid scales) and softer skin (Childs et al). Nevertheless, lungfish are a hardy, interesting fish to keep in an aquarium, and are a good way to observe what eventually evolved into us! The South American lungfish, like other lungfish, are also one of a few fish species left on Earth that belong in the class Sarcopterygii alongside coelacanths.
Me and the rest of the staff at Absolutely Fish are welcome to answer any questions you may have if you wish to inquire about these fascinating fishes of the past. With this new info, I hope you will give these fishes a chance and help take a look into prehistoric life.
Childs, Ken, et al. “South American Lungfish.” Animal World, https://animal-world.com/encyclo/fresh/Misc_PseudoBony/SouthAmericanLungfish.php.
Tokic, Amy. “Gar.” Petguide.com, Petguide, 13 Nov. 2013, https://www.petguide.com/breeds/fish/gar/.
Yang, Alison, and Alison Yang Alison has been interested in fish and aquariums for over five years. When she's not writing about fish you can find her hiking. “Bichir Care 101: Tank Mates, Diet, Size, Types, Etc..” Aquarium Source, 10 May 2020, https://www.aquariumsource.com/bichir/.