Dianema is a genus of armored catfish in the family Callichthyidae, the same family that contains the familiar Corydoras. It sits in the long-whiskered callichthyine lineage alongside genera such as Hoplosternum and Megalechis rather than with Corydoras proper, and both of its species, Dianema longibarbis and Dianema urostriatum, are native to slow-moving Amazon basin waters in Brazil and Peru. Like their relatives, Dianema have bodies sheathed in overlapping bony plates rather than scales, long sensory barbels around the mouth, and the ability to gulp air at the surface and absorb oxygen through a modified section of gut, an adaptation for the low-oxygen, often stagnant backwaters they inhabit.
Dianema longibarbis, the porthole catfish, and Dianema urostriatum, the flagtail catfish, are both well-established and genuinely popular aquarium fish, prized as larger, peaceful, schooling companions in community tanks that also suit smaller Corydoras. Reaching roughly 4–5 in, they are undemanding about water chemistry, forage readily on sinking foods, and are among the more approachable callichthyids for hobbyists wanting to try breeding, since males build bubble nests at the surface and guard the fertilized eggs, a spawning behavior well documented in the hobby literature. Neither species is currently flagged as a conservation concern in the atlas's records.