Arnegard's electric fish

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.

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.

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."

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.

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.

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.

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.