There is much confusion over whether moray eels can live in freshwater because people see an Eel labeled as a "Freshwater Snowflake Moray" in a fish store. Due to the "Snowflake Moray" name, they assume it is a true saltwater Snowflake Moray Eel acclimated to live in freshwater.
Quite simply the answer to this question is no, you cannot put a true saltwater Moray Eel of any kind into fresh or brackish water and expect it to live. With all the research we have done about this, we are not aware of any "true" freshwater Moray Eels.
If the Eel that is being sold is not identified, how are you supposed to care for it? Properly identifying an animal you are thinking of buying is essential to its well-being.
So, how do you identify a Saltwater or Freshwater Snowflake Eel? Simple. The Echidna nebulosa is a saltwater Snowflake Moray Eel. If you see this name attached to an Eel being sold as a "Freshwater Snowflake," it's most likely not one. It has either been grossly misrepresented or misidentified.
Saltwater fish can tolerate the lowering of salinity for short periods of time, which is often done for treating saltwater Ich by means of O.S.T. (Osmotic Shock Therapy), but they cannot remain permanently in these conditions without eventually perishing.
Some Guidance From Shirlie Sharp
To further help clear up the confusion between saltwater and so-called freshwater Eels, we consulted with Shirlie Sharpe. She provided the following information in response to an example of just one of the many e-mails we get on this topic: "You are right; it's nonsense. There aren't any "true" freshwater Moray Eels. However, there are some freshwater Eels that may be misrepresented as such—you know how some pet shops are, they can mislabel a goldfish! In fact, I saw one myself. It looked vaguely like a Snowflake Eel, and the pet shop had a big sign on it "Freshwater Snowflake". In reality, it was a Spiny Eel, Mastocembelus armatus, which is not a true Eel at all. All true freshwater Eels belong to the Family Anguillidae. There's only one freshwater Eel indigenous to the United States: Anguilla rostrata or American Eel (unique name, huh?) What I've seen most often in shops are fish that are called Eels, but in reality, they are not from the Eel Family at all. Among them are "Fire Eels" (Mastacembelus erythrotaenia), "Tiretrack Eels" (Mastacembelus argus), or "Peacock Eels" (Macrognathus aculeatus).
None of these fish are true Eels, and they are definitely not from the saltwater Moray Eel Family."
Identifying Fish By Name
As with many common name references, species identification can sometimes be difficult. To assist with the identification of freshwater Eels, as not to confuse them with saltwater species, here are some resources you can refer to:
Update: Since writing this article it has been brought to our attention that there are some "true" Moray Eels that do inhabit or can adapt to freshwater and/or brackish water environments.