Peacock Eel (Macrognathus siamensis) Care Sheet

Jennifer Doll

Jennifer Doll


Peacock Eel Care Guide

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The peacock eel is a perfect mix between a bichir and a loach and can get along with most large tropical fish. They will need a soft substrate for burrowing and a decent-sized tank to allow them to fully grow to their potential length. However, they are not much harder to keep than most other tropical fish and can make a very interesting addition to the planted aquarium!

Keep reading to find out everything you need to know about peacock eel care and keeping one of these fish in your own aquarium!

Peacock Eel Care Guide


Macrognathus siamensis is commonly known as the peacock eel, zebra spiny eel, or as the spiny peacock eel. The species was first described in 1861 and was previously categorized into the Mastacembelus genus.

While these fish are referred to as eels, they are not true eels; Macrognathus siamensis is part of the Mastacembelidae family while true freshwater eels are part of the Anguillidae family.

Peacock Eel

Natural habitat

Peacock eels are primarily found in Southeast Asia, including the Mekong, Chao Phraya, and Maeklong freshwater river systems. They are most likely to be found on the bottom of slow-moving or standstill waters, buried in the soft substrate with just theirs heads sticking out. There is often dense vegetation in these areas.

These fish tend to feed just before nightfall and can be seen eating insect larvae, worms, and other invertebrates.


Peacock eels are a light yellowish-green color. They have a darker yellow line that runs along most of their body with subtle darker patterning. They also have several dark ‘eyespots’ that have a small white/yellow ring around them towards the end of their body near the caudal fin; these are most likely used to confuse predators and help camouflage.

These fish are known as the spiny eel because of the sharp spines on their dorsal fins! These can easily break through skin so make sure to be careful when handling them or working in the tank. Also, be careful that your spiny eel doesn’t get stuck in an aquarium net if handling the fish.

There is no apparent difference between males and females, though females seem to have an overall thicker body.

How big do peacock eels get?

Full-grown peacock eels can grow to about a foot (30 cm) long, though most of these fish in the aquarium trade average 9 inches (23 cm).

Peacock eel tank requirements

Because of their large size, one peacock eel will need at least 40 gallons (151 L). They are quite shy so they will need plenty of hides in the form of decorations, driftwood, and vegetation.

These tropical fish will also need a sand substrate; a fine gravel can possibly injure your fish and doesn’t allow your plants to grow their roots as easily. Sand also allows your peacock to burrow, which we will discuss later as a part of their behavior.

Peacock eels are tropical fish, so they will need a stable temperature between 73-79° F (23-26° C) with pH between 6.5-7.5.

Peacock eel behavior

While your spiny eel might seem like it could be ferocious, they are actually a very peaceful species.

Because they are mostly nocturnal, you are more likely to see your eel be active at night than during the day. During the day, they like to stay hidden and may even bury themselves in the substrate. However, this could also be a sign that your peacock is stressed and feels threatened. If this happens, try adding more hides to your aquarium and watch to see if other tank mates are the problem.

Since these eels like to burrow in the substrate, you may find that your plants are constantly being uprooted. While this can be annoying, try gently replanting them in an area where your eel if less likely to go. You can also try using floating plants instead.

Peacocks can and will escape from your aquarium. Their streamline body makes them excellent jumpers that can easily fit through small cracks and crevices. Cover your aquarium with a secure lid and check to see that your eel is still in the tank at least once a day.

Are peacock eels aggressive?

For the most part, peacock eels are not aggressive. While they are known to eat small tank mates on the rare occasion, they don’t pose as a threat to many other species.

The only problem you may run into with aggression is when you keep these eels with other Macrognathus siamensis. They tend to become territorial and can cause your fish to become stressed out. Even if enough food is provided for both, it is likely that they will still fight over territory in a small tank.

Every additional peacock eel should have at least 40 gallons (151 L) to itself and more hides should be provided.

Peacock eel tank mates

Many tropical fish can go with peacock eels! The trick to finding the perfect tank mates is by taking note of the size of your eel’s mouth. Whichever fish you end up choosing should not be able to easily be eaten!

While some hobbyists have had success, for the most part, this means that small tetras, guppies, shrimp, and other small invertebrates should be avoided. However, these eels will do great with rasboras, hatchetfish, rainbowfish, and swordtails.

Peacock eel diet

Peacock eels can be picky eaters and won’t usually eat every time they’re fed. Most hobbyists find that their eel only eats about 2-3 times a week. Because of this, it may be best to target feed to ensure that they’re eating enough.

So what do peacock eels eat? Pretty much the same things that they would normally feed on the wild: smaller tropical fish, invertebrates, worms, and insect larvae. It would be best to get an assortment of live, frozen, and freeze-dried foods, like brine shrimp, bloodworms, mosquito larvae, and even feeder fish from time to time.

Most have had success with feeding worms, especially nightcrawlers.

Breeding peacock eels

As of May 2020, these spiny eels have not been bred in the aquarium trade with much success.


If you’re looking for a tropical fish that is out of the ordinary and a little more of a challenge to keep, a peacock eel may be right for you. While you need a larger tank and need to avoid adding smaller fish, this species has a personality all of its own as it digs in the substrate and pokes its head out.

Try target feeding and provide plenty of hides, and your eel will grow to an impressive length.

If you have any questions about spiny care or have kept this species in your own aquarium, don’t hesitate to leave a comment below!

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8 thoughts on “Peacock Eel (Macrognathus siamensis) Care Sheet”

  1. I’ve just got a peacock eel and have been looking for some tank mates for him. He’s in a 180ltr tank about to be upgraded to a 200ltr. Would tiger barbs be a cool tank mate?

    • Hey Jessica!

      Congrats on the eel! Tiger barbs might be a little aggressive for your peacock, though. The harlequin rasbora is a comparable species and would get along great.

  2. Hi there,
    We have a peacock eel, for about a year now. He was healthy and fun until about a week or so ago, when we noticed a bulge in his tummy. He was still pretty active but now he is hiding. Is there anyway he could be a she and those are eggs? We don’t have anything she could breed with. Thanks for the advice

    • It’s very unlikely that these are eggs as peacock eels are almost impossible to breed in captivity, though stranger things have happened. Could you give some more information about your tank setup first? Did you make any big changes recently? Added new livestock? Changed diets?

    • Shrimp seem to be a favorite of many predatory fish! I can’t say I blame them.
      You can also try frozen foods from the grocery store, like mollusks or fish, if you’d like to expand their diet.

    • Hi Shawn,
      There are a few reasons why I’m hesitant to give the OK to this combination. First, both these fish will get very large and are capable of creating a lot of waste that needs to be adequately filtered and closely monitored; in theory, this pairing would only work in much larger tanks, upwards of 150 gallons (567.8 L) with lots of hiding spots and good filtration.
      The second thing I’m worried about is that both fish will grow together at different speeds. In general, oscars tend to grow much faster and larger than spiny eels. This means that potentially, later on, it is very possible that your oscar could eat the eel.
      At the same time, if you get an oscar that is much smaller than the eel, it is also possible that your eel could eat your smaller oscar.
      I’m sure that some hobbyists have made this work, but I would probably go with a more compatible tank mate for either one.


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