Fire Eel (Mastacembelus erythrotaenia): Ultimate Care Guide

The fire eel (Mastacembelus erythrotaenia) is a relatively large species of spiny eel. They dwell in freshwaters in Indonesia, Vietnam, Cambodia, Pakistan, Thailand, and other countries in Southeast Asia. These bottom-dwelling fish are mainly found in slow, buddy rivers and lakes, laying buried in the mud on the bottom. In some areas, in particular Thailand, their numbers have declined due to overfishing for food and the aquarium hobby.

Despite its name, the fire eel is not actually a true eel, but an elongated fish with a pointed snout and an underslung mouth. It belongs to a species of fish called spiny eels, with the name coming from the many small dorsal spines in front of the dorsal fin.

The fire eel is mostly a dark brown/grey color, while the belly is a lighter shade of the same color. Their bodies are marked with several bright red lateral stripes and spots that vary in intensity depending on the age and condition of the fish. Often the anal, pectoral, and dorsal fins have a red edging. Fire eels do not have abdominal fins. Juvenile fish will often have amber/yellow markings that change to a deep red as they mature.

Fire eels are not considered dangerous in the sense that they aren’t known to attack or bite humans. However, their dorsal spines are very sharp and they can do some serious damage if someone attempts to handle them. They also secrete a toxic slime, so any cut they do open can easily become infected if not taken care of immediately.

Fire eels are known to be aggressive, especially towards other fish in the spiny eel family. An adult fire eel will generally tolerate a younger eel in their tank, but another adult will likely be seen as a threat.

Fire Eel (Mastacembelus erythrotaenia)
Fire Eel (Mastacembelus erythrotaenia)

How to Care for Fire Eel

If you have the correct tank setup and environment for them, fire eels can be easy to care for. They are much less demanding of water chemistry than other eels and related fish. These fish are predator fish though, so they need to be kept with tankmates that are large enough that they can’t be eaten.

Fire Eel Water Temperature

The ideal water temperature for fire eels to be kept in is 75-78º F (24-28º C).

Fire Eel Water pH and Hardness

Fire eels require their water to have a pH level of 6.8-7.5, and a hardness of no more than 12.

Fire Eel Size

The size that fire eels will grow to varies greatly depending on whether they are wild, or living in an aquarium. In the wild, they grow to roughly 3.3 feet (roughly 1 meter). In a tank, they only grow to be about 20 inches long (roughly 60 cm).

Fire Eel Lifespan

The lifespan of a fire eel is also greatly affected by whether they are wild or living in a tank. In the wild, they are known to live about 20 years. However, in a tank, they usually only live for about 10 years with proper care.

Fire Eel Tanks Size

The minimum acceptable tank size for a fire eel is roughly 80 gallons. These fish grow quite quickly, so it is best to put them straight into a large tank, rather than starting them in a small tank when they are juvenile and then upgrading – they will outgrow the small tank almost immediately.

Fire Eel Tank Setup

Fire eels are bottom-dwelling fish, so it is important to recreate their natural habitat as closely as possible in your aquarium. This will give your fish the best quality of life, which in turn will give it the longest life expectancy.

The substrate that you use is a very important component. As they burrow in the mud in the wild, fire eels need a substrate that allows them to do the same in their tank. Creating a muddy area using 2-4 inches of fine sand will give them adequate space to burrow. Ensure that it is fine enough so that it doesn’t damage or scratch your fish.

As they are burrowers, try to avoid plants with large roots. When fire eels burrow, they will usually destroy the roots of any plants as they do. Floating plants are best, as not only can your eel not damage them, but they will also help to cut down on light coming into the tank. Fire eels are nocturnal, so keeping some of the natural light out of the tank is important. Plants that can be trained to grow on pieces of bogwood can also be added to their habitat.

Fire eels need lots of hiding spots when they don’t feel like burrowing. Large driftwood, rock caves and other areas it can safely get in and out of are all important additions to their tank as well. PVC pipe can be used as a cheap hiding place, as can a plant pot turned on its side. Anywhere your fire eel can go where it will feel safe and comfortable will be suitable. Make sure to glue your structures together with aquarium-safe glue. This will prevent your eel from accidentally knocking the structure over and harming itself.

Ensure that your tank has a tight-fitting lid with no cracks. Fire eels are known to be escape artists, and will exploit any area it sees that they can escape from. If they do manage to get out of the top of their tank, oftentimes they end up dying on the floor before they are found.

The water in your aquarium also needs to be well-oxygenated and have constant movement. For this reason, powerheads or a quality canister filter are recommended.

Tank lighting should be kept dim, and should be diffused by plants if possible. As fire eels are nocturnal, you may need to adjust the lighting in the tank to create artificial nighttime so that you can enjoy its active periods. This is only possible if natural light can be completely blocked from the tank.

Fire Eel (Mastacembelus erythrotaenia)
Fire Eel (Mastacembelus erythrotaenia). Edited. Llandor, CC BY-SA 3.0

Fire Eel Food and Diet

Fire eels are predatory fish, and in the wild, they prey on small crabs, insect larvae, worms, and snails. Although they are omnivores, they go after meaty sources of protein first.

In an aquarium, fire eels can be fed live food such as bloodworms, small fish, and tubifex. Frozen or dried alternatives are also fine. Adult fire eels can handle larger foods as well, such as earthworms, larger fish, mussels, and live shrimp. Juvenile fire eels do well with small invertebrates such as bloodworms or brine shrimp.

Fire eels can recognize their owners, and will accept food from their hands. This not only helps create a bond with your fish but also makes it easy to monitor the quantity of food they are consuming.

As they grow quite large, they will require a substantial diet to meet their nutritional requirements. Ensuring they have enough food will not only increase their activity levels but also cause them to have more intense coloring.

Fire Eel Breeding

Breeding fire eels in captivity is an incredibly difficult task, which should only be attempted by the most experienced aquarists. If you are going to attempt to breed a pair, familiarize yourself with the information below to give yourself the best chance of success.

Before attempting to breed fire eels, keep in mind that multiple fire eels do not do well in the same tank together. Bringing a pair together has its risks, so consider that before proceeding. You’ll also need quite a large tank for the pair and a separate breeding tank. It is also recommended that you use some special hormonal injections, but even after this it doesn’t guarantee that you’ll be successful. Also, keep in mind that fire eels aren’t able to start reproducing until they are about 2 years old.

To start with, you’ll need to have the perfect conditions in your tank.

  • A spawning tank that is at least 80-100 gallons
  • Water temperature between 28 and 29º C (roughly 82 to 84º F)
  • Water hardness of approximately 10
  • A pH level between 7.0 and 7.2
  • Good tank aeration
  • A quality water filter, large enough for the tank
  • 4 sprayers (one on each corner of the tank)
  • Fish food for the fry (tubifex, insect larvae, and bloodworms)

Set your breeder tank up with water within the parameters above. It is important not to have any substrate in the breeding tank so that you can clean the tank thoroughly and easily. This tank will need to be kept extra clean throughout the entire process. The 4 power filters/sprayers should be located in each corner. This will create powerful filtration, and boost the oxygen content in the water.

During spawning, the male will pursue the female around the tank until she lays her eggs. There will be several spawning sessions, taking place over two days. In this time, she will lay between 700 and 1,000 eggs. It is important to remove the breeding pair from the tank as soon as spawning is finished. Otherwise, they are likely to eat the eggs.

Keep the lighting in the breeding tank low, and carry out a water change of roughly 50 to 60%. Methylene blue can also be added to the water at this time to kill off any bacteria that could affect the eggs.

The eggs will hatch after roughly 48 to 72 hours, and they will feed on their yolk sac for the first 12 days or so. Once the fry become free swimming, they can be fed baby brine, which can be ground up if needed. They can be fed small amounts 5 or 6 times a day during this stage in their lives. It is best to switch off the filter system during this time to prevent the fry from being hurt.

Change out 10% of the water daily and continue to add methylene blue during this period. Metabolic byproducts and food leftovers should be removed as quickly as possible.

If they are well fed, they will grow rather quickly and can reach about 3 inches by the time they are two months old.

Fire Eel Male or Female

Male and female fire eels look very similar, but side by side it isn’t too difficult to tell them apart. The male of the species is generally the smaller of the two sexes, but he will have more vibrate markings than the female does.

Fire Eel Diseases

Always being on the lookout for diseases in your tank is the best way to ensure your eel has a healthy life. The sooner an issue is noticed, the sooner it can be taken care of.

Many freshwater diseases that affect other fish can also affect your fire eel. Changes in their behavior or markings on their bodies will often be the first signs. They can be quite difficult to treat if they do get sick, so avoiding that situation is best. Keeping a safe and hygienic tank for your eel is the best way to do that


Fire eels are susceptible to Ichthyophthirius multifiliis protozoan, or “Ich”. Ich is an external parasite that attaches to a fish’s fins, body, and gills by forming tiny white capsules.

The easiest and most common way to deal with Ich is using store-bought, copper-based treatments available at any pet store. Make sure to follow the correct dosage given on the container.

Bacterial Diseases

Bacterial infections are common in fire eels that are living in poor-quality water. This is the most common cause of bacterial infections in these fish, and can often be avoided with a better water maintenance routine.


Another common affliction of fire eels is infections, usually caused by scratches from burrowing in a substrate that is too rough or coarse. This will irritate the eels’ skin, leading to infection. Make sure to always have a very soft substrate material in their tank.

Fire Eel Tank Mates

While it is advised not to keep more than one fire eel in a tank together, there are other species of fish that can happily co-exist with your fire eel. The general rule is that as long as it can’t eat them, this timid fish will usually leave other fish alone.

African Cichlids and Fire Eel

Fire eels generally stay near the bottom except to feed, so most times cichlids will get along just fine with a fire eel. If the eel does get aggressive, cichlids are usually tough enough to hold their ground, and if the eel doesn’t feel comfortable he will go and hide out of sight for a little while.

Discus -Discus and fire eels are usually fine in the same tank, as long as there is lots of cover for both. Sometimes the discus may not be able to compete with the eel for food, so just keep an eye on how much they are all eating.

Oscars and Fire Eel

While it is possible to keep oscars and fire eels in the same tank, there are several reasons that it isn’t a great idea. Oscars are very territorial, so you would have to have a fairly large tank to make it work, which would need to increase in size exponentially if you wanted more than one oscar. Oscars are also fairly messy fish, and fire eels require well-maintained water. While it can be done, it would take a lot of care to make sure both species were happy and healthy.

Angelfish and Fire Eel

Angelfish are one of the best fish you can select to put in your fire eel tank. They are generally peaceful and timid, and because of their large size, they won’t be seen as food by the eel.

Angelfish should be kept in schools of at least 6 or more, otherwise, they can get a bit territorial and temperamental. However, because they don’t require much tank space at all, your eels’ tank is likely already large enough to house some angelfish as well.

Bichir and Fire Eel

Depending on the species, some bichir fish will only grow to be 12 inches long. However, some can reach 2.5 feet in length, so you need to know what you are getting before making your decision. As long as you get the appropriate-sized fish, bichir can be great tankmates for your fire eel.

Stingray and Fire Eel

As long as there is adequate cover and substrate for your fire eel to hide in, a stingray should be an okay tankmate, as long as they aren’t too large in comparison to the eel. Stingrays can be opportunistic eaters, so if the eel is too small, and the ray isn’t well enough fed, it could take a run at the eel.

Ghost Knife Fish and Fire Eel

Ghost knife fish are bottom dwellers like fire eels are. For this reason, if you are going to have them in the same tanks there needs to be more than enough cover and hiding spots for every fish in the tank. Special attention needs to be taken as well to make sure that all the fish in the tank are getting enough food.

Arowana and Fire Eel

Of all the fish listed, arowana is the most challenging fish to pair with a fire eel. For starters, they can grow to huge sizes, up to 4 feet long. Because of this, they can require a huge tank, up to 250 gallons. They are also highly aggressive fish, so they generally can’t be paired with anything smaller. If you are adding a fire eel into your Arowana tank (or vice versa) make sure there are a lot of places where the eel can safely hide and feel comfortable.

Goldfish and Fire Eel

Goldfish don’t mix well with fire eels for several reasons. First, unless the goldfish are quite large, they will probably be eaten by the fire eel. Secondly, goldfish prefer a cooler water temperature, so either one or the other wouldn’t be in optimal water conditions.

Where to Buy Fire Eel

Fire eel can be found at some large local fish stores, but the easiest way to find them is from an online source. They can be found fairly easily as they are quite a popular fish.

Fire Eel Price

Fire eels range in price from roughly $25 US for a juvenile, all the way up to $200-300 for a healthy, fully-grown fish.

Fire Eel vs Tire Track Eel

Fire eels and tire track eels are both from the same family, Mastacembelidae. Neither is an eel, but actually a fish. They grow to be roughly the same size and eat primarily the same diet.

However, track eels are known to be timider and not aggressive, unlike the fire eel. Their markings aren’t as flashy either, with a dark irregular pattern covering them from head to tail.

Fire Eel vs Peacock Eel

Like fire and track eels, peacock eels are also not eels. They do live in similar water conditions as fire eels, although they are also more tolerant of warmer water as well. They are also burrowers, preferring to burrow under the substrate when they want to hide.

Peacock eels are the smaller of the two, only reaching roughly 12 inches in length. They also aren’t as brightly marked as fire eels, with colors that are usually tan or yellowish-green. They also feature a line of brighter yellow that runs laterally from the snout to the caudal fin.