Most aquarium hobbyists keep a variety of popular freshwater or marine fish and invertebrates. But in recent years, there’s been an exciting new kid in the world of fish farming: freshwater aquarium eels.
The freshwater eel is a fascinating animal that is increasingly finding a place in many home aquariums around the world. There are many different types of eels, some of which are not eels, but fish. Eels come in different sizes, from the tiny 11-inch peacock eel to the massive 8-foot electric eel that might be right for you if you’re an experienced fish keeper with a very large aquarium.
This guide tells you everything you need to know about caring for the mysterious freshwater aquarium eel.
FRESHWATER AQUARIUM EEL – GENERAL DESCRIPTION
|Common name (species)||freshwater aquarium eels|
|level of care||intermediate to advanced|
|Diet||Carnivorous shrimp, crabs, small fish, frozen food, flakes|
|Exercise||Nocturnal, some species are burrowers.|
|Temper||Semi-aggressive but species dependent|
|tank level||Mainly bottom dwellers|
|Minimum tank size||30 gallons|
|Temperature range||Tropical 72-82°F|
|Compatibility||Some species can be housed together but are not suitable for a tank with small fish, invertebrate and amphibian species that will be considered a food source.|
TYPE OF FRESHWATER EELS
Here are nine species of freshwater eels that can make exciting pets for experienced hobbyists.
1. ELECTRIC EEL (ELECTROPHORUS ELECTRICUS)
The famous electric eel is known for its ability to generate an electrical pulse which it uses as a weapon and as a tool to track fast-moving prey. If you come across one of these intimidating creatures, you’ll need to handle your pet with extreme care, as these animals can produce at least 500 volts of electricity.
If you are brave enough to keep an electric eel, you will need an aquarium of at least 200 gallons, as these animals grow to a minimum of eight feet long.
2. PEACOCK EEL (MACROGNATHUS SIAMENSIS)
>The peacock eel is a smaller species of spiny eel, growing to around 11 inches in length and doing well in a 35-gallon tank.
In the wild, the peacock eel lives in calm waters and flooded fields and is found in abundance throughout Asia. These beautiful animals vary in color and pattern, depending on where they come from, but all specimens have three to six decorative «eye spots» along the base of the dorsal fin on the back of the eel. Hence the creature’s common name, Peacock Eel.
3. ZIG-ZAG EEL (MASTACEMBELUS ARMATUS)
The Zig-Zag Eel resembles the Tire Track Eel, and the two species are often confused, although the Zig-Zag Eel is the larger of the two. I recommend that you check carefully to make sure you know which species to take home, as there is a huge difference in size between the two.
The Zig-Zag Eel is a spectacular looking spiny eel that grows to be 35 inches long, so you will need a large tank to house one. However, your efforts will be rewarded with the eel’s 18-year lifespan.
4. BLACK SPOTTED EEL (MASTACEMBELUS DAYI)
The Black Spotted Eel is another spiny eel species that is often confused with the Tire Track Eel and the Zig-Zag Eel as a juvenile. However, when the blackspotted eel matures, it has a pattern of black spots all over its body, hence the other common names of this attractive eel of spotted spiny eel and spotted eel.
The black-spotted eel grows to be 20 inches long and has a lifespan of around 18 years.
5. HALF-BAND SPINEY EEL (MACROGNATHUS CIRCUMCINCTUS)
>The half-banded spiny eel is one of the smallest species of spiny eel, growing to be just under eight inches long. You can keep one of these beautiful eels in a 35-gallon tank, but you should make sure your eel’s habitat has a tight-fitting lid or deck slide, as these slippery characters are consummate escape artists.
These solitary nocturnal eels are found throughout Asia, inhabiting rivers and streams where vegetation is dense and migrating during the dry season to floodplains and channels.
6. ASIAN SWAMP EEL (MONOPTERUS ALBUS)
The Asian swamp eel came to the US as a cheap food source. The eels were raised on fish farms, but many escaped into waterways and are now considered an invasive species in Florida and other coastal regions.
Asian swamp eels grow up to a couple of feet long and need a tank large enough to allow them to stretch out fully. These are very aggressive creatures that must be kept alone and can also snap a piece off their keeper’s fingers, so proceed with caution!
7. PINK PADDLE-TAILED EEL (MORINGUA RAITABORUA)
>The colorful Pink Paddletail Eel is also sold as the Purple Spaghetti Eel. This is a rare species of eel in the hobby and is a very shy creature, spending much of its life buried in the substrate.
This species of eel is a «true eel», belonging to the Moringuidae family of spaghetti or worm eels. Pink Paddletail Eels are carnivorous, but are generally not a threat to larger fish species in a community tank thanks to their very small head and mouth.
8. AFRICAN SPINY EEL (MASTACEMBELUS VANDERWAALI)
>The African spiny eel is also known as the ringed spiny eel. These eels are quite small, reaching around 12 inches in the wild, but only grow to six inches in captivity, making them a good choice for a smaller tank.
These eels are quite shy and spend much of their time in hiding. Although the African Spiny Eel is usually fine with most tank mates of a similar size, they do not get along with others of their own kind and will fight.
9. FIRE EEL (MASTACEMBELUS ERYTHROTAENIA)
>Although fire eels resemble true eels with their snake-like bodies and pointed snouts, these creatures are actually a species of fish.
Fire eels hail from Southeast Asia, where they are found living in slow-flowing muddy lakes and rivers. Fire eels spend much of their time buried in the substrate, coming out at night to feed.
You will need to be careful when cleaning your eel’s tank, as these fish have spines that produce a toxic slime.
ACTIVITY LEVEL / TEMPERAMENT
Eels are generally nocturnal, inhabiting the lower areas of the aquarium. Some species, such as Tire Track, Zig-Zag, and Fire Eels, spend much of their time buried under the substrate with their heads poking out or hidden among plants.
Many species of freshwater aquarium eels recognize their owners, learn when it’s time to eat, and even come out to wait for their meal. Some eels have even been reported to take food from their owner’s hand!
Some species can breathe air and regularly visit the surface of the water to breathe.
COMPATIBILITY AND TANK MATES
With one or two notable exceptions, eels are generally peaceful animals when kept in a single-species tank or community aquarium that features large fish species that the eels will not consider food.
However, eels are carnivorous predators that cannot be safely kept with small fish, crustaceans, amphibians, or mollusks that will likely end up on the menu.
SINGLE SPECIES OPTION
Unfortunately, some eel species do not mix happily once they reach adulthood. Also, thanks to the sheer size of some of the species, the size of an aquarium you would need to house more than one specimen would simply be too large to be practical in most homes.
Before deciding to have more than one eel, always research the species thoroughly first to check how large the animal will be when fully grown and its compatibility with others.
Freshwater aquarium eels are carnivorous and are actually quite easy to feed.
WHAT TO FEED FRESHWATER AQUARIUM EELS
In the wild, freshwater eels eat crabs, shrimp, amphibians, and fish that are small enough for the eel to swallow. Generally, the larger the eel, the more prey it can catch. So keep this in mind if you are going to keep your eel in a community tank.
Eels raised in aquariums can be fed live foods, such as shrimp, feeder fish, and Thai micro-crabs. Eels will also take to frozen meaty foods, but be sure to thaw them first in a small amount of tank water. The sinking pellets that are formulated for carnivorous fish and eels can also be fed as a supplement to the basic meaty diet of eels. Fresh fish can be a protein-rich addition to the menu.
To add variety, try including fresh or frozen bloodworms, earthworms, and blackworms.
HOW MUCH AND HOW OFTEN TO FEED
Eels only need to be fed twice a week and some specimens may not accept foods offered as often. So don’t panic if your eels only eat once every two to three weeks.
If you’re not home or at the ideal time to feed your eels, it’s worth investing in an automatic fish feeder with a timer. Simply load the feeder hopper with a small portion of food and set the timer to deliver the food at a predetermined time.
Freshwater aquarium eels are relatively easy to care for, as long as you provide them with the right living conditions.
Aquarium eels vary in size, but we do not recommend keeping any species of eel in a tank smaller than 35 gallons.
As a general rule of thumb, you should allow 10 gallons of water for every 15-inch eel. So a species larger than around 25 inches will need a minimum of 20 gallons of water to get comfortable.
Some species of eel are accomplished jumpers, and virtually all are excellent escape artists, squirming through the smallest hole in the aquarium lid. For example, swamp eels can also jump and breathe air, crossing great distances on land in the wild. Therefore, the carpet in your living room is not afraid of them!
As with any species of fish, your eels will do best if you keep them in a tank that mimics their natural environment as closely as possible. In the case of aquarium eels, these creatures are found throughout the world in many different habitats, including temperate and tropical climates.
Again, before purchasing an aquarium eel, research its habitat carefully and replicate it in your aquarium.
The substrate that best suits your choice of eel will depend on where your eel comes from. If you choose a burrow species, you should use a soft sandy substrate or peat. Most eels are bare or have very small scales to protect their bodies, so a soft substrate is a must.
Eels live on the bottom and most species appreciate having a place to hide. So you need to include caves, rocks, overhangs, twisted roots, and driftwood in your setup. You can also include a piece of plastic or terracotta pipe that the eels will use as a hiding place.
Again, to reproduce the well-vegetated natural environment of the eels, dense, heavy planting is the way to go. Java Fern, American Eelgrass, and Elodea are all good species to use, and you should include some floating plants that will help diffuse lighting in the aquarium.
During periods of activity, eels appreciate plenty of room to swim, so don’t clutter the tank with too much decoration.
Eels typically inhabit slow-moving waters with very dense vegetation where the animals spend much of their time hiding or hunting. For that reason, the flow in the tank should be slow to moderate. However, eels generate a fair amount of waste, so you need a very efficient filtration system to keep your water clean and sanitary. If necessary, dampen the flow with plants or rocks.
Eels come from many different regions and climates, so you should carefully research the individual requirements of the species you have chosen before setting up your tank.
The most popular freshwater aquarium eels are tropical animals that need a water temperature between 72° and 82° Fahrenheit.
pH range and water hardness
Water hardness between 5 and 15 dKH with a pH in the range of 6.5 to 7.5 suits most eel species.
Regardless of the species of eel you have chosen, they all need low lighting to feel comfortable and safe. If the lighting in the aquarium is too bright, you will most likely not see much of your eel as it will hide until the lights go out for the night.
Use a series of floating plants to diffuse and dim the light, but remember that many species of eel can breathe air, so leave part of the water’s surface unobstructed for that purpose.
Once you have properly set up the water conditions and tank environment, freshwater eels are fairly easy to care for. That said, it is necessary to keep the tank clean with well-oxygenated water.
VACUUM THE SUBSTRATE
Eels produce a large amount of waste, so it is essential that you vacuum the aquarium to clean out uneaten food, debris, and decaying plant material. In addition to cleaning the substrate, pay attention to the areas around the bases of the plants, under decorations, and in the corners of the tank.
Keep your plants tidy and prevent excessive growth by trimming dead leaves and stems.
MAKE PARTIAL WATER CHANGES
In addition to vacuuming the tank, you should do partial 30% water changes every two weeks to keep ammonia, nitrates, and nitrates at acceptable levels. Ideally, ammonia and nitrite levels should be zero, and you don’t want more than 20 ppm nitrate in the water.
MAINTAIN FILTER CARTRIDGES / FILTER MEDIA
Your filter will only work properly if it is free of sludge so water can flow freely over the media. Therefore, flush the filter media in tank water about once a month and replace used media and filter cartridges as needed.
Start by putting together everything you need for your eel aquarium:
How to set up your tank:
- Clean the aquarium substrate under running water to remove loose dust and debris.
- When the water runs clear, place the substrate in your aquarium to a depth of at least 3 inches, more if your eel is a burrower.
- Set up and place your filtration unit and heater in the tank, but don’t turn them on yet.
- Next, fill your tank with unconditioned tap water. Tap water contains ammonia that the bacteria in the biological filter media require to start the nitrogen cycle before introducing the fish, so don’t add conditioner at this time.
- Place an upside down container on the substrate and pour the water over it so as not to disturb the substrate.
- Wash your tank decorations to remove dust and place them in your aquarium.
- Cut off damaged leaves and dead stems from your live plants, then plant them in your tank. Leave enough space between the plants so they have room to grow and spread.
- Turn on the heater and filter, and let the aquarium run for at least ten days before introducing your eels. Before adding your cattle, I recommend that you test the tank water to ensure that the ammonia, nitrite, and nitrate levels are acceptable.
HEALTH AND SICKNESS
Freshwater eels are prone to many common fish diseases, parasites, and fungi, largely because they don’t have scales. However, providing excellent quality water is by far the best way to prevent disease outbreaks in an eel tank.
SIGNS OF GOOD HEALTH
It can be difficult to tell if your eel is unwell, as they spend much of their time inactive in hiding places or lurking among plants.
However, eels enjoy swimming in open water once they have settled into their new home.
Warning signs that could indicate health problems may be brewing include:
- poor appetite
- inflammations and ulcers.
- Hitting or rubbing against tank substrate and decorations.
COMMON HEALTH PROBLEMS AND TREATMENT
|Health problem||Symptoms or causes||suggested action|
|Ich (white spot disease)||Ich is the most common disease in aquarium-raised fish and eels. The disease is caused by a protozoan parasite, Ichthyophthirius multifiliis. Ich usually appears as a telltale splatter of tiny white spots on the eel’s body. Animals with Ich rub or hit solid surfaces in the tank.||Raise the water temperature to 82o F for three days and use an over-the-counter Ich treatment.|
|Fungal infections (gill rot, branchiononephritis)||White cottony growths.||Quarantine the eel if it is in a community facility and treat the tank with an antifungal treatment.|
|Bacterial infections||Ulceration and red spots on the skin of the eel, tumors under the jaw (cauliflower disease)||Quarantine the eel if it is in a community facility and treat the tank with an antibacterial treatment.|
Not much is known about the reproduction of freshwater eels and, at the time of this writing, they are not widely bred in captivity.
That’s largely because the most popular aquarium eels available to hobbyists live in freshwater but spawn in the ocean.
Many species of freshwater eel are commonly seen in fish stores, and you can find most species available through online dealers.
The price of eels varies depending on the rarity of the species and the size of the eel. For example, Tire Track Eels can be purchased for around $20, while Electric Eels cost upwards of $300.
There are many species of eel to consider, each with their own specific requirements, but I hope this guide has given you a better idea of what you’re up against if you’re considering keeping these fascinating creatures.
If you found this article useful, please share it with your like-minded hobbyists and tell us about your freshwater eel in the comment box below. We would love to hear your story!