Aquarium eels

The aquarium fish sold as eels fall into two groups: freshwater spiny eels like the fire eel, and the saltwater moray eels of a FOWLR tank. Both are secretive, mostly nocturnal and famous for escaping, so a tight lid and places to hide come first. The freshwater moray is the odd one out, a moray from fresh and brackish rivers that needs a tank of its own. Each profile lists adult size, tank size and diet.

Tank size: 42–291 gal; 42 gal (160 L) to 291 gal (1,100 L); half the list needs 79 gal (300 L) or more
Temperature: 73–82°F; 23–28°C, most of the list
pH: 6.0–7.5; Most of the list
Difficulty: 2 easy; 24 medium · 8 difficult
Temperament: 1 peaceful; 30 mostly peaceful · 3 aggressive

34 species

Spiny eels are not eels

Fire eels, peacock eels, tire tracks and zebra spiny eels are spiny eels, a family of freshwater fish that only look the part. They breathe with ordinary gills, they have small fins, and they spend the day buried to the eyes in sand. Most of the Macrognathus here stay manageable at 7.5 to 11.8 inches (19 to 30 cm). The peacock and zebra spiny eels reach 11.8 inches (30 cm), and the half-banded 7.9 inches (20 cm). The one-stripe spiny eel outgrows the rest at 23.6 inches (60 cm) and lists 119 gallons (450 liters). The big Mastacembelus are another matter. A fire eel reaches 39.4 inches (100 cm) and lists a 132 gallon (500 liter) tank. A tire track eel reaches 27.6 inches (70 cm) and lists 119 gallons (450 liters).

Sand, hiding places and a lid

Most spiny eels want a soft sand bed deep enough to disappear into and a pipe or root to hide under. Brichard's spiny eel wants smooth boulders over sand and strong current instead. The Malawi and the two Tanganyika spiny eels want piled rock with crevices as well as sand. Every spiny eel needs a lid without gaps, because they will find the hole you did not know you had. They feed at night on worms and frozen food and rarely take flake, so plan on bloodworms, blackworms and chopped shrimp dropped near their hiding spot after the lights go off. Tank mates should be too big to swallow and calm enough not to steal every meal.

Moray eels for a saltwater tank

Six of the seven morays on the page are marine, and the freshwater moray eel lives in fresh and brackish rivers. The snowflake eel is the usual first moray, rated easy, at 39.4 inches (100 cm) in a 50 gallon (189 liter) tank. The zebra moray is a pebble-toothed crab eater that reaches 59.1 inches (150 cm), and it is the one eel here marked peaceful. The golden dwarf moray stays at 11.8 inches (30 cm) but still lists 65 gallons (246 liters), more than the snowflake eel. The ribbon eel is the trap: beautiful, rated difficult, and famous for refusing food. The dragon and honeycomb morays are big, aggressive and for the dedicated predator tank.

By the numbers

Smallest

Largest

Easiest to keep

FAQ

Common questions

Are spiny eels true eels?

No. They are the family Mastacembelidae, freshwater fish with an eel shape. The morays on this page are true eels. Both groups burrow, hide and escape through gaps in the lid.

What do aquarium eels eat?

Spiny eels take worms, bloodworms and other frozen or live food at night and mostly ignore flake. Morays eat meaty food, chopped fish and shrimp, offered on a feeding stick. The ribbon eel often refuses everything, which is why it is rated difficult.

Do eels escape from aquariums?

Yes, and it is the usual way they die. Fit a tight lid, cover the gaps around pipes and cables, and keep the water an inch or two below the rim.

What size tank does a fire eel need?

A fire eel lists 132 gallons (500 liters) for an adult of 39.4 inches (100 cm). A juvenile in a 30 gallon tank is on borrowed time.

Are moray eels reef safe?

With caution. They leave corals alone but eat shrimp, crabs and any fish that fits in the mouth, and they knock rockwork over. The zebra moray is the gentlest of the group.

Can spiny eels live with other fish?

Most are marked mostly peaceful, and anything small enough to swallow is food. The peacock, zebra and half-banded spiny eels do fine with calm mid-sized fish too big to eat. The fire eel, the tire-track eel and the other big Mastacembelus need tank mates too large to be prey. The one-stripe spiny eel grows big enough to swallow small fish, so it needs large tank mates too.

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