Rummynose Tetra

Rummynose Tetra (Petitella rhodostoma) is a species of fish in the family Acestrorhamphidae. It is native to South America (lower Amazon and Orinoco basins). The rummynose tetra is the tightest-schooling small tetra in the hobby and the one most worth buying in numbers. A group of twenty moves as a single object, turning together, with twenty red noses and twenty black-and-white striped tails. Start with which fish you are actually buying. Three similar species are traded under this name, and all three now sit in the genus Petitella, though shop labels still say Hemigrammus: Petitella bleheri, the firehead tetra, which is the one most commonly sold; Petitella rhodostoma, the true rummynose; and Petitella georgiae, the false rummynose. They are told apart by how far the red extends — in P. bleheri it continues past the gill covers onto the body — and by the caudal peduncle markings, with the first two carrying dark blotches at both the top and the bottom. It reaches 50 mm standard length. The red nose does work as a condition gauge, with an important qualification covered below.