A spiny eel is not actually a member of the eel family—it is a type of fish. There are two different species of fish that have this nickname. One type lives in freshwater, while the other is a saltwater fish. Both of them have long, thin, eel-like bodies, but unlike true eels, they have three distinct spines on their dorsal fins.
The saltwater eel is from the family Notacanthidae. It swims close to the sea floor. It feeds on bottom-dwelling animals such as anemones and worms, which burrow in the mud. The marine spiny eel is further divided into 11 more species. Each of these fish are characterized by different fin-to body ratios, numbers of spines, and jaw shapes. Some have narrow jaws, while others have ones which are blunt, wide, and toothy.
The freshwater spiny eel is of the family Mastacembelidae, which includes swamp eels. It is characterized by its long, ribbon-like body and its needlelike snout. This type of spiny eel is known as an aquarium fish. Several species have beautiful coloring. The peacock eel in particular is prized for its green and blue coloring.
In the wild, these freshwater fish tend to live in swamps and brackish water, feeding off of worms and other tiny animals. For this reason, their aquariums will need to be furnished with plants or rocks where the eel can hide during the day. Being a nocturnal species, the eel will then come out in the evening for feeding.
The spiny eel will not eat pellets or flakes if kept in captivity. Its food needs to be alive and moving in order for it to take an interest. Most often, owners will feed their eels bloodworm, larvae, or tiny crustaceans. A spiny eel is also more sociable than most fish in that it is not shy about approaching people for food and will eat out of someone's hand when it is placed in the tank.
When in an aquarium, spiny eels do not often spawn. This may be due to difficulties the fish have mating rather than any kind of inherent impossibility. There are few resources for those looking to breed the fish, and some guides to keeping them in aquariums will identify them incorrectly. It can also be difficult to transition the fast-moving eels to a separate aquarium where the spawning can take place. If they are in a tank with other fish, their eggs may be eaten before they can hatch.