Peacock Eel: A Complete Freshwater Care and Setup Manual

Originating in the slow-moving rivers of Thailand, Cambodia, and Vietnam, the Macrognathus genus of spiny eels earns its common name from a striking row of small dorsal fin spines running along its back. The species most often sold under that common name tops out near 12 inches, behaves almost strictly at night, and burrows into soft substrate by day. its belong to the Mastacembelidae family, not the true eel order Anguilliformes, which changes how you handle them, treat them for disease, and protect them from escape.

This manual walks you through every stage of keeping a peacock eel healthy, from choosing the right tank size and substrate to selecting peaceful tank mates and coaxing a shy nocturnal carnivore to feed.

Meet the Peacock Eel and Its Spiny Eel Relatives

The fish most stores call a peacock eel is almost always Macrognathus siamensis, a tubular, snake-shaped fish built around a pointed snout and a row of sharp dorsal fin spines that rise when the animal is stressed or handled. Those spines are why the group carries the common name “spiny eel,” a feature that separates them from true eels and from knifefish, which look similar but lack the spine row. The spines are not venomous, but they snag on coarse nets and can puncture a thin plastic bag during shipping.

Because peacock eels are not true eels, several common care assumptions break down. Standard eel medications and salt dips behave differently on spiny eels than on marine eels or morays. Copper-based ich treatments stress them badly, so most experienced keepers rely on heat-based or herbal ich remedies rather than copper. The elongated body also flexes through gaps that would stop a thicker fish, which matters the moment you choose a lid and filter setup.

Three species often sold as “peacock eel”

Stores rarely distinguish between the Macrognathus species, so the fish you bring home may be any of the three below. All three need similar care, but adult size and temperament differ enough to be worth knowing.

Species	Common name	Adult length	Key visual cue
Macrognathus siamensis	Siamese spiny eel / peacock eel	10 to 12 in	3 to 5 pale ocelli (eye-spots) along the dorsal ridge
Macrognathus pancalus	Barred spiny eel	7 to 9 in	Vertical bars along the flanks, smaller body
Macrognathus circumcinctus	Half-banded spiny eel	7 to 10 in	Dark saddle-like bands on a paler belly

Identifying your fish at purchase sets a realistic size expectation and prevents the common mistake of buying a 3-inch juvenile for a 20-gallon tank that will be outgrown within two years.

Lifespan and what it means in practice

A healthy peacock eel in a stable tank routinely lives 8 to 18 years, with most well-kept specimens landing between 10 and 14. That span is longer than many dogs, longer than most community fish, and long enough to outlast periods when a hobbyist loses interest. Treat the purchase the way you would a long-lived reptile, not a tetra you can replace for a few dollars. Plan for the tank to stay set up, for the filter to keep running during travel, and for someone to feed the fish if you are away for a week.

Deciding Whether a Peacock Eel Fits Your Tank and Experience

Most failed it setups fail for the same reason: the keeper wanted a visible, daytime-active oddball and bought a nocturnal burrower instead. The fish is rarely the problem. Run through this honest self-assessment before you spend the money.

• ▸Experience level: Comfortable with cycling a tank, testing water, and quarantining new fish. First-time fishkeepers can keep one, but only after they have already cycled at least one tank successfully.
• ▸Tank size: 36 gallons is the practical minimum, 40 to 55 gallons is better, and anything under 30 gallons will stunt a fish that wants to patrol a 3-foot floor.
• ▸Floor area over height: A 36-gallon long (36 by 12 by 16) outperforms a 30-gallon tall because the spiny eel lives on the bottom, not in the water column.
• ▸Patience for slow acclimation: Willing to wait 2 to 6 weeks for a new specimen to begin eating in front of you, and to feed after lights out for months if needed.
• ▸Tolerance for a shy pet: Happy to own a fish you may only see at night, with brief daytime glimpses when it crosses open sand.

Two situations should make you pass on the purchase for now. If you want a centerpiece fish that greets you at the front glass, choose a gourami or a peaceful cichlid instead. If your current tank is heavily stocked with fast-feeding tetras, rasboras, or barbs, the eel will be outcompeted at every meal until you can move it into a quieter setup. Holding off for a few months while you rehome faster fish protects both your money and the new animal.

Designing a Tank That Mimics a Slow Southeast Asian River

Once the fish matches your experience, the tank has to match the fish. The it’s wild habitat is a slow, shaded, plant-choked river with a silted bottom, and every design choice below copies one feature of that environment.

Substrate, plants, and décor

Use fine sand as the substrate, not gravel, at a depth of 2 to 3 inches. The fish burrows fully, and any sharp edge will scrape its belly, opening a path for bacterial infection. Pool filter sand or blasting sand from a hardware store works well and costs a fraction of aquarium-labeled products.

Layer driftwood, leaf litter (Indian almond or catappa leaves are standard), and dense plant cover on top of the sand. Java fern tied to wood, Anubias on the floor, and floating plants like water sprite cut the light and create the dusk-like conditions the species prefers. Each piece of wood and each plant mass also serves as a daytime retreat when the eel is not buried.

Water parameters and lighting

Target a temperature of 73 to 82°F, a pH between 6.5 and 7.5, and general hardness around 4 to 15 dGH. The fish tolerates a wide range, so stability matters more than hitting a specific number. Match whatever your tap water produces, then leave it alone unless the fish is breeding or visibly stressed.

“Match the water you have, not the water you read about online. A it kept at a steady pH of 7.4 will outperform one bounced between 6.8 and 7.6 every time you do a water change.

Lighting should be dim, either through a low-wattage LED on a separate timer or by floating plants that filter the room light into a soft green wash. A bright, fully lit display tank keeps the eel hidden for weeks on end.

Filtration and escape-proofing

A canister filter or a hang-on-back unit rated for 50 to 75 gallons on a 36 to 55 gallon tank gives clean water without the violent flow that stresses bottom-dwellers. Aim the outlet across the long axis of the tank and break the surface with a piece of driftwood or a sponge pre-filter so the eel is not pushed around the floor. Cover every intake with a sponge pre-filter to keep a curious nose out of the impeller.

Escape-proofing is the single most important piece of setup, and it is where most hobbyists cut corners. The fish can pass through any opening wider than its head, which is roughly the diameter of a pencil for an adult. Use these specific tactics:

With the tank escape-proofed and softened, the harder behavioral challenge begins: convincing a shy predator to actually eat on your schedule.

• ▸Lid weight: A glass lid with a clamp or a thick acrylic top is mandatory. The fish pushes lightweight hoods out of the way.
• ▸Cord and airline gaps: Route power cords and air lines through a single drilled hole, then seal around the cable with a foam gasket or black silicone.
• ▸Filter intake openings: Cover the intake slots of hang-on-back filters with fine mesh or a sponge pre-filter. A 0.5-inch gap is enough room for an adult to slip in and die inside the filter.
• ▸Canister hose leaks: Check hose connections monthly. A loose union that drips onto the floor is the same shape as a it, and the fish will follow it.

Feeding a Carnivore That Refuses to Be Rushed

Feeding is where most new keepers lose confidence. A it that ignores food for the first week is normal; one that ignores food for six weeks is a setup problem, not a fish problem. Understanding why the fish waits, and what to do about it, is the difference between a thriving specimen and a slow decline.

Building a workable diet

Staple foods include frozen bloodworms, frozen brine shrimp, frozen daphnia, and finely chopped seafood such as rinsed shrimp, scallop, or white fish. Sinking carnivore pellets and freeze-dried krill help get a settled fish onto prepared food, but rarely work on a new import. A varied mix of frozen proteins outperforms any single food, because the fish recognizes the smell and movement of several different items.

Live foods bridge the gap when frozen is refused. Blackworms, small earthworms chopped to size, and live brine shrimp are the standard tools. Use live food as an acclimation step for the first two to four weeks, then taper it off in favor of frozen as the fish begins to recognize the smell of thawed bloodworms hitting the water.

Outsmarting faster tank mates

The single most common cause of a it losing weight is competition, not pickiness. Tetras, danios, and barbs will vacuum up every piece of food before the eel even reaches it. Three techniques solve this:

1. 1Tong feeding: Hold a cluster of bloodworms in feeding tongs and wiggle it near the eel’s head. The motion triggers a strike even in shy fish.
2. 2Glass dish method: Sink a small shallow dish (a condiment dish works) into the sand and drop food into the same spot every night. The eel learns the location, and the dish keeps the food contained.
3. 3After-lights-out feeding: Drop the room lights, leave only the room glow from a hallway, and add food 30 minutes later. A nocturnal species fed on its own schedule eats without competition from diurnal fish.

A well-fed it shows a gently rounded belly, a full body cross-section, and a calm posture when it emerges at night. A fish that is slowly declining shows a concave belly, a visible spine ridge, and a head that looks disproportionately large. Weighing the fish is impractical for most keepers, so visual checks every two weeks are the realistic monitoring tool.

Choosing Tank Mates Without Triggering Predation or Competition

The ideal tank mate is a peaceful mid- or top-dwelling species that ignores the substrate layer and does not harass the eel at night. Several reliable groups work, and several common community staples do not.

Compatible tank mates	Incompatible or risky choices
Larger rasboras (scissortail, giant)	Small tetras under 1.5 in (will be eaten at night)
Peaceful gouramis (dwarf, pearl, honey)	Dwarf shrimp colonies (food, not companions)
Mid-sized barbs that ignore the floor (cherry, gold)	Active bottom feeders (loaches, corys share the space and stress the eel)
Small rainbowfish	Fin-nippers like tiger barbs and serpae tetras
Single peaceful cichlid (keyhole, kribensis)	Large or aggressive cichlids (oscars, jack dempseys)
Other spiny eels in a 75-gallon-plus setup	Aggressive catfish like red-tailed or large pictus

The bottom row on the left is worth a closer look. A 75-gallon tank with two its of similar size, dim lighting, and dense cover often produces quiet, dignified displays, and the species-only setup removes the competition problem entirely. The bottom row on the right is the one that catches people out. A it does not intentionally hunt small fish, but a 1-inch neon tetra that drifts past its snout at 2 a.m. is a meal, not a neighbor. Treat any fish small enough to fit in the eel’s mouth as prey, and any fish large enough to bully the eel as a threat.

“Compatibility fails rarely happen during the day. Watch the tank with a red light after lights out for an hour during the first week. Active chasing, body-slams, or the eel being pinned into a corner signals a pairing that has to be broken up.

Three signs a pairing is failing, even when daytime behavior looks calm: the eel loses weight while the other fish stays fat, the eel hides constantly and never appears at night, and you find bite marks on the eel’s tail or the long tubular snout.

Acclimation, Long-Term Health, and Honest Breeding Limits

Once the tank is set up and the food plan is in place, the last stage is the first 30 days with the fish and the maintenance rhythm that follows. A it that survives import and acclimation well will rarely cause problems if the water stays clean and the food keeps coming.

Drip acclimation and the first month

Use a slow drip acclimation over 60 to 90 minutes, longer than for most community fish, because the eel is sensitive to pH and temperature swings and arrives already stressed from shipping. Match the bag water to your tank water gradually, then net the fish out rather than pouring the bag water into the tank. Dim the lights for the first 48 hours, and avoid any tank work that disturbs the sand or moves décor during that window.

Normal settling behavior in the first 30 days looks like this: hiding constantly for the first week, brief nighttime forays by week two, accepting food on a tong or in a dish by week three, and emerging in low light during the day by week four. Red flags that need action include open-mouth breathing at the surface, refusal of any food for longer than six weeks, visible fungus or white patches, and a hollow belly that worsens despite offering food. A fish that breathes at the surface within the first 24 hours is usually suffering from ammonia exposure in shipping and needs a slow water change rather than a treatment.

Common diseases and what actually works

The three most common health problems are ich, bacterial infections from belly abrasions, and stress-related wasting. Ich shows up as small white dots, typically after a temperature drop or a new fish introduction. Treat with a heat-based method (raise the tank to 86°F for 10 to 14 days) rather than copper, which spiny eels tolerate poorly. Bacterial infections from sand abrasions show as red patches on the belly or along the jaw, and respond best to clean water and a broad-spectrum antibiotic in a hospital tank. Wasting is almost always a feeding problem masked as illness, and the fix is competition control, not medication.

Breeding in home aquariums

Documented home breeding events remain scarce, with the handful of successful cases occurring almost exclusively in large outdoor ponds rather than indoor tanks. Triggering spawning requires a wet and dry season simulation, a temperature drop followed by a rise, and a group of mature fish. Hobbyists should not expect fry from a pair in a 55-gallon, and any seller claiming captive-bred juveniles for under ten dollars each is mislabeling wild-caught imports. Treat the fish as a long-term display pet, not a breeding project.

Your final decision framework

Before you click “buy,” answer three questions. Does your tank meet the 36-gallon minimum with a sand substrate and a sealed lid. Have you kept a cycled tank stable for at least three months without a major loss. And are you prepared to feed the fish after lights out for several months while it settles. Three yes answers and the species is a strong match. Two yes and one no means wait until the missing piece is in place. One or zero and the right move is to keep a hardier oddball and come back to the it when your setup is ready.

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