Arnegard's electric fish
Petrocephalus arnegardi
Arnegard's electric fish features a slender body, pale coloration, and distinctive elongated dorsal and anal fins with a faint lateral line.
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About the Arnegard's electric fish
This is a little Congo River elephantfish (a weakly electric mormyrid) that cruises the lower parts of the tank and navigates the world with its electric sense. It stays small (around 9 cm) and has a clean silvery look with three dark marks that make it pretty easy to pick out among Petrocephalus.
Also known as
Quick Facts
Size
9 cm
Temperament
Peaceful
Difficulty
Advanced
Min Tank Size
30 gallons
Lifespan
6-10 years
Origin
Central Africa (Congo River basin)
Diet
Micro-predator/insectivore - small live and frozen foods (bloodworms, blackworms, brine shrimp, daphnia), plus quality micro-pellets once settled
Water Parameters
24-28°C
6-7.5
2-12 dGH
Need a heater for this species?
This species needs 24-28°C in a 30 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Go bigger than you think: a 30-40 gallon with a long footprint, dim lighting, and lots of broken line-of-sight (roots, rock piles, leaf litter) keeps them from getting stressed and snappy.
- Keep the water soft and on the acidic side - think pH around 6.0-7.0, low KH, and steady temps around 76-80F; they hate sudden swings more than slightly "off" numbers.
- Run a sponge prefilter on your intake and keep flow moderate - they like oxygen but not a washing machine, and a strong intake will suck up a curious night-roamer.
- Feed after lights out: blackworms, daphnia, baby shrimp, chopped bloodworms, and small sinking carnivore pellets once they recognize them; they do way better with several small meals than one big dump.
- Skip nippy or hyper tankmates (barbs, most danios) and avoid big predators; they do best with calm fish that ignore them, like small Synodontis, peaceful cichlids that are not bitey, or mellow tetras that stay midwater.
- Do not mix with other mormyrids unless the tank is big and you know what you are doing - they can harass each other nonstop, especially if there are not enough hides.
- Watch for "mystery" weight loss: they can look fine but get outcompeted at feeding time, so target feed with a turkey baster and make sure food hits the bottom where they hunt.
- Breeding is rare in home tanks, but if you want to try, simulate rainy season with a cool water change and heavier feeding, then give dense plants or mop-like cover for eggs and be ready to pull adults since they will snack.
Compatibility
Good Tankmates
- Small, chill schooling fish that stay midwater like ember tetras, rummynose, or black neons - they do their own thing and dont mess with the electric fish cruising around at dusk
- Peaceful pencilfish (Nannostomus) - calm, top-to-mid swimmers, not bitey, and they wont compete hard for the same hiding spots
- Corydoras catfish in a proper group - they hang on the bottom, ignore everybody, and dont bother the Petrocephalus while its snooping around for food
- Small, mellow Loricariids like bristlenose (Ancistrus) or otocinclus - good cleanup crew, mostly nocturnal-ish like the elephantnose types, and generally drama-free
- Peaceful dwarf cichlids like Apistogramma or rams - works if the tank is not cramped and you give plenty of wood and caves so nobody feels like they have to claim the whole bottom
- Calm, not-too-big African butterfly fish can work if the tank is covered tight - they stick to the surface and usually leave the electric fish alone (just dont mix with tiny fry-sized tankmates)
Avoid
- Fin-nippers and hyper stuff like tiger barbs, some danios, or serpae tetras - theyll stress the electric fish out and pester it when it wants to cruise quietly
- Aggressive or territorial cichlids (most Mbuna, big Central Americans) - too pushy, too much competition for caves, and they turn the tank into constant chase mode
- Big predatory fish like bichirs, large catfish, or anything that can mouth it - Petrocephalus are peaceful and can get bullied or straight up eaten when the lights go down
- Other elephantnose or mormyrids in small tanks - they can get weirdly competitive with each other over food and personal space unless youve got a big footprint and lots of hiding spots
Where they come from
Arnegard's electric fish (Petrocephalus arnegardi) is a little African mormyrid from the Congo basin region. In the wild they spend a lot of time in slower water, backwaters, and weedy edges where the light is low and the bottom is soft. They are built for cruising and "sniffing" around with their electric sense more than for sprinting.
These are weakly electric fish. They are not going to shock you, but they do use an electric organ and a sensitive "radar" to find food and read their surroundings. That has big consequences for how you set up the tank.
Setting up their tank
If you want this species to settle in, think dim, roomy, and calm. I have had the best luck starting with a bigger footprint than you would expect for a small fish. They cruise, and they stress out fast if they feel exposed.
- Tank size: I would start at 30 gallons minimum for one, and 40-55+ if you want a small group (recommended). Footprint matters more than height.
- Substrate: fine sand is your friend. They sift and nose around, and coarse gravel can beat up their mouth and belly.
- Hardscape: driftwood, roots, leaf litter, and caves/tubes. Give them multiple "parking spots" so they are not forced to share one hide.
- Plants: live plants help a lot, especially floaters to knock the light down. You do not need a jungle, just broken sight lines.
- Flow and filtration: gentle to moderate flow. Strong blasting current tends to keep them pinned and skittish. Use a prefilter sponge on intakes.
- Lighting: keep it subdued. Bright lights with no cover usually equals a fish that only comes out at 2 a.m.
- Water: stable, clean freshwater. Slightly acidic to neutral is a safe starting zone. Keep nitrate low and do regular water changes.
Use your aquascape to create lanes and pockets. They like to cruise along edges (wood lines, plant lines), then dip into cover. A bare glass box makes them act like they're being hunted.
Skip sharp decor and rough rock piles. They are not clumsy, but they do a lot of close-quarters probing in the dark. Any sharp edge will eventually win.
They do not love sudden changes. If you can, drip acclimate and keep the first week quiet: low light, minimal hands-in-tank time, and feed small amounts more often rather than dumping in a big meal.
What to feed them
Feeding is the make-or-break part with Petrocephalus. Many new imports ignore flakes and pellets for a while, and they can fade fast if you do not get food into them early.
- Best starters: live or frozen blackworms, bloodworms, daphnia, baby brine shrimp (for smaller individuals), and chopped earthworm.
- Reliable staples once eating: frozen foods (bloodworms, mysis, brine shrimp) and good quality sinking micro-pellets if you can convert them.
- How to feed: target feed after lights are dim or out. I use a turkey baster to drop food right in their cruising path.
- Frequency: smaller meals 1-2 times daily beats one big dump. They are natural "grazer-hunters."
If a new fish is acting shy, feed with the room lights off and the tank lights dim. They relax fast in low light, and you'll see them start to hunt with that little probing snout.
Do not assume they are eating just because food disappears. Tankmates will happily clean up. Watch the fish: you want to see it actively picking and chewing, not just hovering.
How they behave and who they get along with
They are usually peaceful, but they are not "community fish" in the easy sense. They communicate and navigate by electricity, and a busy, boisterous tank can keep them pinned in hiding.
With their own kind, expect some posturing and chasing, especially in tight quarters. In a bigger tank with lots of cover, a small group can work well and you will see more natural behavior. If you cram them, they get edgy and you will see nipped fins and constant hiding.
- Good tankmates: calm, non-nippy fish that like similar water and do not hog the bottom. Think small to medium peaceful tetras, pencilfish, hatchetfish, calm barbs, and some gentle dwarf cichlids (species dependent).
- Risky tankmates: fin nippers (tiger barbs, many larger barbs), hyperactive feeders, aggressive cichlids, and big predatory catfish.
- Bottom competition: watch loaches and heavy-feeding catfish. They can outcompete Petrocephalus at mealtime and stress them just by being all over the substrate.
They are more confident in dim tanks with cover. If you keep them in bright, open setups, you will mostly own an expensive hiding fish.
Breeding tips
Breeding Petrocephalus in home tanks is possible but not something I would call routine. Most success stories involve a settled group, seasonal cues, and a tank that has been stable for a long time.
- Start with a group: 5-8 in a bigger, well-structured tank gives you a shot at mixed sexes without guessing.
- Conditioning: heavy feeding on live/frozen foods for weeks. They need to look robust, not pinched.
- Season cues: many keepers mimic a "rainy season" with slightly cooler water changes, then gradually warmer, plus lots of fresh water changes and increased feeding.
- Spawning setup: dense plants (including fine-leaved or spawning mops), leaf litter, and gentle flow. Eggs are typically scattered and not guarded.
- Fry food: if you get fry, be ready with tiny live foods (infusoria, rotifers, vinegar eels) before transitioning to baby brine shrimp.
Do not chase breeding by constantly messing with parameters. These fish reward stability. Sudden swings and nonstop tinkering usually end with stress and disease.
Common problems to watch for
Most issues with this species trace back to stress, food, or water quality. They are hardy once settled, but new or stressed individuals can go downhill fast.
- Not eating: the big one. New imports often refuse dry food. Start with live/frozen, feed in low light, and target feed.
- Skin parasites and ich: stressed fish show it first. Quarantine helps a lot. Treat gently and keep oxygenation up during meds.
- Weight loss despite "feeding": usually competition at the bottom or the fish is not actually getting the food. Separate for a week if you need to.
- Damaged mouth/belly: almost always from rough substrate or sharp decor.
- Chronic hiding and skittishness: too much light, too little cover, or tankmates that are too intense.
- Sudden deaths after water changes: big parameter swings. Match temperature and avoid huge changes unless you know your tap water is stable.
Be careful with copper and harsh medications. Mormyrids can be sensitive, and they also rely on their sensory systems. If you have to medicate, go slow, increase aeration, and watch behavior closely.
If you want one piece of advice to keep them long term: build the tank around their comfort (dim, sand, cover) and take feeding seriously the first month. Once they associate your routine with food, they get a lot bolder and you will actually see what makes them special.
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