Flathead long-whiskered catfish

Where they come from

Megalonema platycephalum is a South American river catfish. You see it tied to the big, warm lowland systems (think broad rivers and floodplains) where the water is usually tannin-stained, full of leaf litter, and the fish spend a lot of time hugging the bottom and structure.

The whole "long-whiskered" thing is real. Those barbels are built for feeling their way around in dim water, which tells you a lot about how to set them up at home.

Setting up their tank

Give this fish floor space first, not height. They are bottom cruisers, and they get stressed if they feel exposed. If you set up a bright, bare tank, you will mostly own an empty aquarium and a nervous catfish.

• Tank size: I would not bother under 55 gallons, and 75+ is a much nicer long-term home because they need room to patrol the bottom.
• Substrate: smooth sand is my pick. Fine gravel can work, but sand is easier on the barbels and encourages natural rooting around.
• Hiding spots: driftwood, root tangles, and a couple of caves (PVC works if you hide it). Provide more than one so it can choose.
• Lighting: keep it subdued. Floating plants or tannins from wood/leaf litter help a lot.
• Flow and filtration: decent turnover with steady current is good, but avoid blasting the bottom. They appreciate clean, oxygen-rich water.

Water-wise, aim for typical tropical South American community parameters: warm, soft-to-medium water, stable pH, and low nitrate. Stability beats chasing numbers. Do regular water changes and keep the bottom from turning into a mulm swamp.

What to feed them

They eat like a catfish: meaty, sinking foods, mostly at night. Mine ignored flakes completely but went straight for anything that hit the bottom and smelled like food.

• Staples: quality sinking carnivore pellets or wafers (not the cheap starchy stuff).
• Frozen foods: bloodworms, mysis, chopped krill, brine shrimp, and especially earthworm pieces.
• Occasional: live blackworms or live earthworms if you can get them clean and safe.
• Skip as a habit: feeder fish (disease risk and they can make your catfish picky).

Feed small portions more often rather than one huge dump. Big catfish meals can foul the tank fast, and these guys are happy to keep eating if you keep offering.

How they behave and who they get along with

They are generally chill, a little shy, and most active in low light. The main "attitude" issue is size-based: if it fits in the mouth, it might become a midnight snack.

• Good tankmates: medium-to-large peaceful fish that stay midwater (bigger tetras, silver dollars, many larger cichlids that are not hyper-aggressive, peaceful characins).
• Use caution: other bottom dwellers (they may compete for caves and food), slow fish that sleep on the bottom, and anything tiny.
• Avoid: nano fish, delicate long-finned fish that rest low, and super-aggressive cichlids that will claim every cave.

One more thing: they can spook hard. A tight-fitting lid matters. If something startles them, they go from statue to torpedo in a heartbeat.

Breeding tips

Breeding Megalonema platycephalum in home aquariums is not something you see often. Sexing is not obvious, and most imports are just kept as single specimens or in mixed communities where spawning behavior never really gets going.

If you want to take a swing at it, think like a river fish: heavier feeding for conditioning, lots of cover, and a seasonal "rainy period" simulation with cooler, larger water changes and a bump in flow and oxygen. Even then, I would treat it as a long shot and enjoy them for what they are.

Common problems to watch for

• Barbel wear or infection: usually from sharp gravel, dirty substrate, or constant digging through waste. Sand and a clean bottom fix most of it.
• Skin scrapes: they wedge into tight spots. Give them caves that fit the whole body, not just the head.
• Starving in a busy community: they are polite eaters. If faster fish steal everything, target feed with tongs or drop food right at their cave after lights out.
• Bloat/constipation: too much dry food and not enough variety. Mix in frozen foods and do not overfeed pellets.
• Ich and other parasites on new imports: quarantine if you can. Wild-caught fish can arrive stressed and sensitive.

The biggest success factor with this species is simple: a calm, shady tank with clean sand and predictable feeding. Do that, and you will get a confident fish that actually comes out instead of hiding forever.