Notched mud carp

Where they come from

Notched mud carp (Henicorhynchus entmema) are Southeast Asian river fish. Think big, warm floodplains and turbid channels where the water moves, the bottom is soft, and there is always a lot of tiny food in suspension. They are built for cruising and grazing all day, not hovering around a rock like a cichlid.

Setting up their tank

This is one of those fish that looks manageable in the store and then turns into a constant-motion, high-oxygen, high-waste machine at home. Plan the tank around adult size and activity. If you try to squeeze them into a medium tank, you will be fighting water quality and stress behavior nonstop.

• Tank size: I would not keep a group in anything under 5 ft long, and 6 ft is better. They use the whole length.
• Group size: 5+ if you can. Singles get skittish and pace. In a group they settle into a rhythm.
• Filtration: big canister or sump with lots of bio media. Add a powerhead or two for flow and oxygen.
• Temperature: mid-70s F works well. They handle warm water, but hot + low oxygen is where trouble starts.
• Water: neutral-ish is fine. Stability matters more than chasing a number.
• Substrate: sand or smooth fine gravel. They mouth the bottom a lot.
• Decor: open swimming space first, then use driftwood/rocks along the edges to break sightlines.
• Lid: tight. They can jump when spooked.

What to feed them

These guys are basically living vacuum cleaners for fine foods. In my tanks they did best when I fed smaller portions more often, instead of one big dump of food that either spikes waste or gets bullied away by faster fish.

• Staple: quality sinking pellets or wafers that soften but do not explode into mush right away.
• Greens: blanched spinach, zucchini, green beans. Clip it down so it stays put.
• Protein: frozen daphnia, brine shrimp, cyclops, chopped bloodworms (not as the only food).
• Natural grazing: let some biofilm develop on wood and rocks. They will pick all day.
• Feeding frequency: 2-3 small feeds daily if your filtration can handle it.

How they behave and who they get along with

Temperament-wise they are pretty peaceful, but they are not quiet fish. They are active, always on the move, and they do a lot of startle-dashing if the tank is cramped or the lighting is harsh. Give them room and they calm down a lot.

They are also strong feeders. They are not aggressive like barbs nipping fins, but they will outcompete slow, delicate fish just by being everywhere at once.

• Good tankmates: other robust river fish that like flow (larger barbs, danios, some loaches), medium-large peaceful catfish, sturdy rainbowfish.
• Avoid: long-finned fish (they can get stressed by the constant activity), tiny nano fish, slow bottom dwellers that get shoved off food.
• Plants: expect them to uproot weakly planted stems. Tough plants tied to wood or rocks do better than rooted carpets.
• Behavior note: they school loosely. If you only keep 1-2, they tend to glass-surf and spook easily.

Breeding tips

Breeding them in a home aquarium is not something most hobbyists pull off. In the wild they are seasonal spawners tied to rising water and floodplain conditions. In tanks, you usually just end up with very well-fed adults and no eggs.

If you want to try anyway, the closest thing I have seen work with similar river cyprinids is a big group, heavy conditioning, then a big cool-water change paired with stronger flow and extra fine foods. Even then, expect eggs to be scattered and quickly eaten.

• Use a large group so you get natural spawning behavior.
• Condition for a few weeks on mixed frozen foods plus good pellets.
• Try a large (30-50%) water change with slightly cooler water and increased flow.
• If you ever see chasing and trembling, add a spawning mop or a mesh egg trap because they will eat eggs.
• Have a separate grow-out ready. Fry would need tiny foods (infusoria, rotifers, then baby brine).

Common problems to watch for

Most issues I have seen with notched mud carp trace back to three things: not enough space, not enough oxygen, and not staying on top of waste. They are forgiving of pH numbers but not forgiving of a dirty, low-flow tank.

• Constant glass-surfing: usually too small a tank, too bright, too little cover, or they are kept in too small a group.
• Gasping or hanging near the surface: oxygen issue. Add surface agitation and flow, clean clogged media, check temperature.
• Rapid weight loss: internal parasites are common in wild fish. Quarantine and consider deworming if they do not gain weight despite eating.
• Frayed fins or scrapes: they spook and slam into decor. Remove sharp rocks, keep open lanes for swimming, use sand.
• Bloat/constipation: too many dry foods without roughage. Add greens and vary foods; soak pellets if needed.
• Ammonia/nitrite spikes: they produce a lot of waste. Do not add a whole group to a new tank, and do not overclean bio media.