Freshwater moray eels have been called "The Fish That Doesn't Exist." When most of us picture a moray, we picture the green moray (Gymnothorax funebris), the ten foot long giant that haunts coral reefs of the Western Atlantic.
Gymnothorax funebris
Many marine fish keepers are also very familiar with smaller species such as the Snowflake Eel (Echidna nebulosa), a crustacean eating moray from the Indian Ocean and the Indo-Pacific.
Echidna nebulosa
There are many other species of moray eel that are very familiar to both divers and fish-keepers alike, but most are purely saltwater fishes. Many people believe that the entire family lives entirely in saltwater, hence the term "Fish That Doesn't Exist."
"The Fish That Doesn't Exist," however, does indeed exist. Indeed, there are many of these non-existant eels, but only four are ever seen in the aquarium trade. Freshwater morays should really not be considered freshwater, but brackish, and all of them also thrive in full marine water. The four species range in size from just over one foot, to over three feet long, and all are predatory. Freshwater morays are mostly of the genus Gymnothorax, a group that eats primarily fish. These fish have long, slightly recurved teeth perfect for gripping fish. The three Gymnothorax are all potentially very similar in appearance, with the young being grey, brown, and olive in color.
The dark moray, Gymnothorax afer, an eel reaching 40 inches in length from the Eastern Atlantic, is a dark brown eel that is the most easy to differentiate from the others. It has a high dorsal fin, and a large head. This fish is a solid brown color with no markings and is more commonly seen in marine tanks than in brackish or freshwater tanks. It should never be placed in freshwater, in fact, as it is a brackish to marine eel. It is also the least common of the four.
Gymnothorax afer
The freshwater snowflake eel, Gymnothorax tile, reaches about 26 inches in length and is often confused with both Gymnothorax polyuranodon and Echidna rhodochilus. This is probably because all three are collected from the same region, the Indo-West Pacific. Although seen for sale in fresh water, this is a brackish water fish just and is not found in freshwater in the wild. This fish has small yellow, white, or gold freckles across a brown or grey body. It also has a high dorsal fin, but an unusually small head for a member of the genus. This is the most available of the four species mentioned here.
Gymnothorax tile
The freshwater moray eel, Gymnothorax polyuranodon, which is most often confused with the aformentioned eel, is a primarily brackish fish that can also live in both pure marine and pure freshwater conditions. It grows to approximatly 36 inches in length, and differs greatly in both coloration and body shape. Rather than the freckels seen on G. tile, this fish exhibits large elongated black and tan blotches over its body. It has an unusually small head as well. In addition, the dorsal fin is subdued by a shroud of thick skin.
Gymnothorax polyuranodon
The last eel is a member of the genus Echidna, as is the chainlink moray (Echidna catenata) and the snowflake moray. These fish have thick, sharp teeth deeply recurved, thus giving them a nearly flat surface which is ideal for crushing the shells of invertebrates. The white-cheecked moray, Echidna rhodochilus, grows only to 13 inches, and like G. polyuranodon, is completely amphidromous. These fish have a greenish brown body with yellow or olive fins, a short dorsal fin, and a small head with a rather blunt snout, which helps to differentiate it from the Gymnothorax species. The white-cheecked moray has a redish nose with pink or white dots on it, as well as a white or pink patch on either side of the head.
Echidna rhodochilus
These are not fish for the beginner aquarist. They are picky, delecate for a moray, and often times never eat. They should nor be kept with sharp substrates and must have plenty of places to hide. A good lair can be made by piling driftwood and lace limestone together. Although two can live without salt, none of these four eels should be considered freshwater. They all ought to be kept in brackish conditions, with the exception of G. afer, which ideally belongs in a marine aquarium. They are all voracious predators and are not to be trusted with small fish or with delacate tankmates. Ideal tankmates include chromides, cichlids of the infrafamily Ptychochromini from Madagascar, Gangetic leaf fish, sailfin mollies, sleepers, puffers, violet gobies, and freshwater flatfish. Note that not all those fish will work with larger specimens.
In short, these fish are are wonderful and interesting creatures, but require advanced care and are not recommended for anyone but experienced brackish or marine fishkeepers. Don't make this your first brackish fish. I hope this helps should anyone here choose to buy one of these eels.
Pictures taken from FishBase, except for Echidna rhodochilus, taken from the author's personal collection from the author's fish tanks.
Many marine fish keepers are also very familiar with smaller species such as the Snowflake Eel (Echidna nebulosa), a crustacean eating moray from the Indian Ocean and the Indo-Pacific.
There are many other species of moray eel that are very familiar to both divers and fish-keepers alike, but most are purely saltwater fishes. Many people believe that the entire family lives entirely in saltwater, hence the term "Fish That Doesn't Exist."
"The Fish That Doesn't Exist," however, does indeed exist. Indeed, there are many of these non-existant eels, but only four are ever seen in the aquarium trade. Freshwater morays should really not be considered freshwater, but brackish, and all of them also thrive in full marine water. The four species range in size from just over one foot, to over three feet long, and all are predatory. Freshwater morays are mostly of the genus Gymnothorax, a group that eats primarily fish. These fish have long, slightly recurved teeth perfect for gripping fish. The three Gymnothorax are all potentially very similar in appearance, with the young being grey, brown, and olive in color.
The dark moray, Gymnothorax afer, an eel reaching 40 inches in length from the Eastern Atlantic, is a dark brown eel that is the most easy to differentiate from the others. It has a high dorsal fin, and a large head. This fish is a solid brown color with no markings and is more commonly seen in marine tanks than in brackish or freshwater tanks. It should never be placed in freshwater, in fact, as it is a brackish to marine eel. It is also the least common of the four.
The freshwater snowflake eel, Gymnothorax tile, reaches about 26 inches in length and is often confused with both Gymnothorax polyuranodon and Echidna rhodochilus. This is probably because all three are collected from the same region, the Indo-West Pacific. Although seen for sale in fresh water, this is a brackish water fish just and is not found in freshwater in the wild. This fish has small yellow, white, or gold freckles across a brown or grey body. It also has a high dorsal fin, but an unusually small head for a member of the genus. This is the most available of the four species mentioned here.
The freshwater moray eel, Gymnothorax polyuranodon, which is most often confused with the aformentioned eel, is a primarily brackish fish that can also live in both pure marine and pure freshwater conditions. It grows to approximatly 36 inches in length, and differs greatly in both coloration and body shape. Rather than the freckels seen on G. tile, this fish exhibits large elongated black and tan blotches over its body. It has an unusually small head as well. In addition, the dorsal fin is subdued by a shroud of thick skin.
The last eel is a member of the genus Echidna, as is the chainlink moray (Echidna catenata) and the snowflake moray. These fish have thick, sharp teeth deeply recurved, thus giving them a nearly flat surface which is ideal for crushing the shells of invertebrates. The white-cheecked moray, Echidna rhodochilus, grows only to 13 inches, and like G. polyuranodon, is completely amphidromous. These fish have a greenish brown body with yellow or olive fins, a short dorsal fin, and a small head with a rather blunt snout, which helps to differentiate it from the Gymnothorax species. The white-cheecked moray has a redish nose with pink or white dots on it, as well as a white or pink patch on either side of the head.
These are not fish for the beginner aquarist. They are picky, delecate for a moray, and often times never eat. They should nor be kept with sharp substrates and must have plenty of places to hide. A good lair can be made by piling driftwood and lace limestone together. Although two can live without salt, none of these four eels should be considered freshwater. They all ought to be kept in brackish conditions, with the exception of G. afer, which ideally belongs in a marine aquarium. They are all voracious predators and are not to be trusted with small fish or with delacate tankmates. Ideal tankmates include chromides, cichlids of the infrafamily Ptychochromini from Madagascar, Gangetic leaf fish, sailfin mollies, sleepers, puffers, violet gobies, and freshwater flatfish. Note that not all those fish will work with larger specimens.
In short, these fish are are wonderful and interesting creatures, but require advanced care and are not recommended for anyone but experienced brackish or marine fishkeepers. Don't make this your first brackish fish. I hope this helps should anyone here choose to buy one of these eels.
Pictures taken from FishBase, except for Echidna rhodochilus, taken from the author's personal collection from the author's fish tanks.
Last edited:
