Aquarium Tropical Fish Articles
Aquarium Eels have long skinny bodies, and are great at escaping from the aquarium!
Aquarium Eels are a group of Eels and Eel-like fishes that all have long snake-like bodies and similar diets. They are also very clever fish. They have a most singular habit of being escape artists, wiggling through even the smallest hole in an aquarium cover.
Fish referred to as 'Freshwater Eels' in the aquarium hobby and included here belong to various families. Some of them are true eels found in the order of Anuilliformes, like the American Eel and the European Eel members of the family Anguillidae, and the Worm Eels or Spaghetti Eels of the family Moringuidae.
Others are not true eels, but are eel-type fish. These include the well known Spiny Eels of the Mastacembelidae Family. Although these are not actually eels they surely they look like them. There is also the well known Electric Eel Electrophorus electricus. It too is not a true eel. It is actually a Naked-backed Knifefish belonging to the family Gymnotidae, bBut we are including it here because of its common "Eel" name. And then there are those fascinating Rubber Eels, which are actually aquatic amphibians!
The Eel list below includes popular types of aquarium eels and eel-like fish, as well lesser known varieties. Each fish guide has a description of the species, its place of origin, habitats and behaviors, as well as fish care to successful maintain them in an aquarium. Fish pictures are also provided within each fish guide to help with identification, and to aid in choosing the best type of Aquarium Eel for your freshwater or brackish water fish tank.
For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care
Fish that are called 'eels' have a long snake-like body. Most are without a separate dorsal and pelvic fin, rather their fins appear merge together with the tail fin to form a continuous fin fringe. Most also have small gill opens, often just a single gill slit at the throat. Eels vary in size but the average size of most species is from between 12 - 36 inches (30 - 90 cm) in length. In their native regions many of these fish are considered a good tasting food.
There is only one order of fish classified as true freshwater eels, this is the Anuilliformes Order of eels.
- Freshwater Eels
The Anuilliformes Order of eels contains freshwater eels in two families, the family Anguillidae and the family Moringuidae.
- Anguillidae Family
The Anguillidae family consists of a single genus, Anguilla, which has 19 species and 6 subspecies. Including are the American Eel Anguilla rostrata, which is the only true eel in North America, and the European Eel Anguilla anguilla. These true eels live their entire lives in freshwater, but return to the ocean to spawn.
- Moringuidae Family
The other family, Moringuidae, contains the Worm Eels or Spaghetti Eels. There are 14 species contained in 2 general. These freshwater eels have very skinny, long cylindrical bodies and range in size from just under 6 inches (15 cm) in length up to 55 inches (140 cm). They are found in shallow tropical waters throughout the world.
- Anguillidae Family
- Saltwater Eels
All other families in the Anuilliformes Order of eels are saltwater eels, including the Moray eels in the Muraenidae family. See the Marine Eels category for these species.
- Freshwater/Saltwater Eels
Some 'true eels' in the Muraenidae family can be kept as freshwater eels due to the fact that they can occur in both freshwater and saltwater environments at different times of their lives, like the popular Snowflake Eel. But these fish are more commonly sold as saltwater eels.
Aquarium eels also include many so-called 'freshwater eels' that are not true eels. Yet they are all commonly called "eels" in the aquarium industry. Other Eel-type fishes include:
- Swamp Eels
The Swamp Eels are members of Synbranchiformes Order which contains 3 families.
- Spiny Eels - Mastacembelidae Family
The Mastacembelidae family contains the well known Spiny Eels. They are not actually eels but surely they look like them.
- Swamp Eels - Synbranchidae Family
- Earthworm Eels - Chaudhuriidae Family
- Spiny Eels - Mastacembelidae Family
- Electric Eel
There is also the well known Electric Eel Electrophorus electricus. The Electric Eel is also not a true eel, as it actually a Naked-backed Knifefish belonging to the family Gymnotidae. But we are including it here because of its common "Eel" name.
- Rubber Eel
Those fascinating Rubber Eels, are actually aquatic amphibians!
Fish often referred to as Eels:
Finally there are some fish that are often referred to as eels but that are not. These fish don't usually have the word 'eel' in their common name. These include such critters as Bichers and Ropefish, Knifefish, Eel Catfish, Lungfish, and Slimy Eels. Most of these are included in their own categories, see: Bichers and Ropefish, Knifefish, Catfish, and Unusual Fish to find them.
Eels and eel-like fish are mostly carnivores. They mainly get active in the evening or after dark and are mostly bottom feeders. Primarily they will eat live food such as small crustaceans, mosquito larvae, worms, and fish. Some of these fish, such as the Spiny Eels and the Freshwater Eels, are also carrion eaters and may adapt to eating freeze dried and frozen proteins such as tubifex and bloodworms. Eels only need to be fed a couple of times a week and some may refuse food offered that often, eating only once every two or three weeks.
Generally quite hardy, eels and eel-like fish adapt to most aquarium conditions. For the most part these fish are bottom dwellers, but many species are able to breathe air at the surface directly from the atmosphere. Some eels are great jumpers and most of them are excellent escape artists, getting through any available hole in the aquarium cover. Being both jumpers and able to breathe air, Swamp Eels have been known to cross great distances of land.
Eels like to hide in caves or holes but also need plenty of space to swim. Many species, especially the Spiny Eels, also enjoy burrowing into the substrate. Because most eels are naked or have very small scales protecting their bodies it is important that the substrate is soft, such as fine sand and peat. They do best in a dimly lit aquarium or one with floating plants to help subdue the light.
Though most eels can be kept together as juveniles they may become quarrelsome if they are over crowded. They become aggressive solitary predators as adults and will eat smaller and slower moving fish. They should only be kept with species of a similar size.
Many of the true eels are only suitable to a home aquarium as juveniles because as adults they simply become too large. The life span also varies depending on the individual species.
There is little known about the reproduction of most of these fish and they are not currently bred in captivity.
Two Freshwater Eels in the Anguillidae family available to aquarists, the European Eel Anguilla anguilla and the American Eel Anguilla rostrata (the only true eel in North America), live in fresh water but spawn in the ocean.
The Swamp Eels in the family Synbranchidae are often found in swamps and ponds. They spawn in shallow waters, laying hundreds of free floating eggs that gather together in bubbles.