Hyphessobrycon (Paracheirodon) innesi, the renowned Neon Tetra
Paracheirodon innesi (Neon Tetra). In 1936 visitors to the Shedd Aquarium in Chicago lined up to view exotic Neon Tetras for the first time. They had been named by Dr Myers that year for W.T. Innes, and I'm just about the last to have given up the cherished old name of Hyphessobrycon innesi. The fish had been collected in the Amazon and shipped to Germany. Then they were flown back across the Atlantic in the dirigible airship "Hindenburg". Neon Tetras are now many generations removed from the clear and blackwater streams where they were first discovered and exported. Their home territory is the lower Putumayo River and the Leticia-Tabatinga district where the borders of Peru, Colombia and Brazil come together along the upper Amazon. They can be found as far down the Amazon drainage as São Paulo de Olivença. For years, while Neon Tetras were being flown out of Leticia, the exact locality from which they were being collected was kept tightly controlled as a "trade secret;" it was even withheld from the scientists who formally described them. The location wasn't revealed til about 1960. That was the year that Jacques Géry separated out a new genus, Paracheirodon, from the grab-bag of taxa lumped together as "Hyphessobrycon"; he designated P. innesi as the type species of the newly identified genus.
All but a tiny percentage of Neons on the U.S. market now come from Hong Kong, where cooler weather encourages more prolific breeding than in Malaysia and Singapore. In a brief 1998 bio of Neon Tetras by Dr. William Fink's biology student at U. of Michigan, Emily Couture, (now deleted from the Web alas), she emphasized how little is known about Neon Tetras in their native habitat, and incidentally remarked on the disease susceptibility of mass-produced Neons that are farmed in continuously medicated water in southeast Asia. In 1998 Prof. Frank Chapman and some colleagues at the University of Florida wrote an article "Controlled spawning of the neon tetra" in the journal Progressive Fish Culturist, to encourage Florida fish farmers to take up the domestic production of this popular species. Dr Chapman's fish spawned successfully in two-week cycles for a year; his fry received rotifers and an infusion of boiled egg yolk as their first foods. Robert J. Goldstein spoke to Prof. Chapman while doing preparation for his article, "Breeding Neon Tetras" for Aquarium Fish, July 2000, and Chapman expanded on his published thoughts about why Neons were such meager producers, when aquarists got them to spawn. Chapman thinks that the Asian fish are fed chow laced with testosterone, a common "color enhancer." The testosterone makes the young fishes color up prematurely, so that they're marketable at barely half an inch, whereas unjuiced juveniles don't begin to show their colors til they are a bit larger. Chapman thinks that testosterone is decreasing females' fertility. Of course, once you have raised your own tank-bred Neon Tetras, female fertility will be back to normal in the next generation. So, the next time you're at a club auction event, you might consider paying a premium for a member's tank-raised Neon Tetras.
When you get them home, you'd do best to start breeding them right away, for these are all but annual fish in their native surroundings. In controlled laboratory conditions, Dr Dariusz Kucharczy and his Polish team determined that Neon Tetras produce viable gametes in fewer than half a dozen breeding cycles, and that if they are spawned again in 15 to 20 days the results were better (more surviving 12-day-old fry) than after a longer wait (see an abstract of Dr Kucharczy's findings).
But good news follows Chapman's work at the University of Florida; much healthier neons from Florida fish farms are beginning to come onto the U.S. retail market. A January 2001 U. of Florida press release announced that the breeding "secrets" were slightly acidic, soft water at 77oF. Hmm. No surprises for you there!
Paracheirodon innesi at FishBase. Paracheirodon innesi at Wikipedia. Paracheirodon innesi at SeriouslyFish.