Anhanga pygmy pencil catfish

Where they come from

Potamoglanis anhanga is one of those tiny Amazonian catfish that feels more like a secret than a common aquarium fish. They come from Brazil in the Amazon basin, living in small streams and flooded margins where the water is warm, soft, and often stained with tannins. Think leaf litter, tangled roots, and lots of micro-prey drifting by.

Setting up their tank

For these, I plan the tank around two things: calm water and tons of cover. A busy community tank with strong flow will make them vanish and slowly waste away. A species tank or very quiet nano works way better.

• Tank size: 10-20 gallons is fine for a small group, but bigger is easier to keep stable
• Keep them in a group: 6+ if you can, they act way less stressed
• Soft, warm water: aim roughly 76-82F, low to moderate hardness, pH on the acidic to neutral side
• Filtration: gentle sponge filter or a baffled HOB. You want clean water without a river-current
• Substrate: fine sand or very smooth gravel. They spend time nosing around
• Cover: leaf litter (catappa/oak), small caves, cholla, root tangles, dense plants, moss
• Lighting: dim or broken up with floaters. Bright tanks make them hide

Stability matters more than chasing numbers. If your tank is new-ish, skip this species for now. They do best in a mature setup where the biofilm and microfauna are already established.

What to feed them

They are micro-predators. Mine ignored flakes and most pellets. Once they recognize live or frozen foods, they eat with a lot more confidence, but you usually have to meet them where they are: down low, near cover, and often after lights-out.

• Go-to foods: live baby brine shrimp, microworms, grindal worms, small daphnia
• Frozen: cyclops, baby brine shrimp, finely chopped blackworms, small bloodworms (sparingly)
• Prepared: tiny sinking micro-pellets can work once they are settled, but do not count on it at first
• Feed timing: dusk or after lights out, and target the bottom with a pipette or turkey baster

If you keep them with faster fish, you will probably need to target-feed. I like using a long pipette to blow a little cloud of cyclops and baby brine right into their leaf litter zone. After a week or two of that, they learn the routine.

How they behave and who they get along with

Anhanga pygmy pencil catfish are peaceful, but they are also easy to intimidate. They spend a lot of time hovering low, darting between leaves and roots. In a comfortable tank, you will see them perched and hunting in short bursts rather than constantly hiding.

• Best tankmates: none (species tank), or very calm nano fish that will not outcompete them
• OK choices: tiny pencilfish, small ember-type tetras, very gentle rasboras, small ottos (only if your tank can support them)
• Avoid: anything boisterous, anything that charges food, and anything big enough to view them as snacks
• Inverts: usually fine with shrimp, but they will take baby shrimp if they can catch them

Breeding tips

Breeding in the home aquarium is not something I would call predictable. It is possible you will get surprise fry in a mature, heavily leaf-littered tank, but do not buy them expecting a straightforward breeding project.

If you want to try anyway, I would focus on conditioning and providing safe egg/fry zones rather than forcing it. Feed heavy on live foods for a few weeks, do frequent small water changes with slightly cooler, softer water, and keep the tank quiet. Dense moss, fine roots, and piles of leaves give eggs and fry a chance to avoid being hoovered up by tankmates (or even by the adults).

Common problems to watch for

Most losses with this species come from slow starvation, stress from too much activity, or the tank being too new. They are not a beginner fish, not because they are aggressive or weird, but because they are easy to accidentally neglect.

• Starvation: they never compete well. Fix with target feeding and calmer tankmates (or none)
• Getting blown around: too much flow keeps them from foraging. Baffle outlets and use a sponge filter
• Bright, bare tanks: they stay hidden and eat poorly. Add leaves, plants, and shaded zones
• New tank syndrome: they do poorly in immature setups. Wait for a tank that is a few months old at least
• Wasting/skinny syndrome: can be internal parasites. Quarantine new arrivals, consider deworming if weight never improves despite good feeding
• Sensitivity to meds: use gentle dosing and extra aeration. Avoid nuking the biofilter in a small tank

If you are patient and you set the tank up like a little Amazon leaf-litter corner, they are ridiculously rewarding. The first time you catch them actively hunting through the leaves under dim light, you will get why people obsess over these tiny catfish.