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February 09, 2012

The largest black water river in the world, the Rio Negro, is located in South America. Though the name means “black river”, the color it resembles is more like tea. This dark complexion is probably caused by the humic acid, which comes from decaying vegetation near the bottom of the stream. The natives of Colombia, where the water sources begin, call it the Rio Guainia. Here in Colombia, the waterways flow along the Rio Orinoco and the magnificent Amazon. This path will cross with the Rio Vaupes (Uaupes) and the Rio Guaviare. The river at one point drops into the Rio Solimões in Venezuela to form the Amazon River South near Manaus, Brazil. From the months of November through March, the water level in most places can be as low as 6 feet, but as the rainy season arrives, the water rises and at certain areas it can be as wide as 19 miles.

In forested streams of black water tributaries throughout the valleys of the Rio Orinoco and the Rio Negro, you will find swarms of Paracheirodon simulans “Green Neon Tetras” swimming in massive schools. In these slow moving areas, the water is stained dark brown and can have a pH value of 3.0! Because the trees create a giant canopy light is very dim here. Their bright blue stripe creates a signal to other Green Neons that allows the group to stay together even in the faintest of light. In an aquarium, I recommend keeping them in a planted tank with some floating plants to make them feel more at home. This will help to bring the petite 1”+ fish out and actively seeking some frozen daphnia or finely crushed flake food. As the Green Neon is a shoaling fish by nature you should keep in them in large groups.

Paracheirodon simulans

Paracheirodon simulans

The family name Gasteropelecidae comes from the Greek word “gaster” for “stomach” and “pelekis” for “axe”. This is an obvious reference to the Rio Negro’s floodplain fish’s body shape known now as Carnegiella marthae “Black-Winged Hatchetfishes”. These 1.5” fish use this body structure, as well as specially adapted muscles in their pectoral fins, to propel themselves out of the water in search of insects or when frightened by a potential predator. Because of this “leaping” behavior, the tank should be well covered. I have seen hatchets escape from even the slightest of cracks. The Black-Winged Hatchetfish does have a special diet. A variety of floating or live foods is certainly preferred over dried flakes. These peaceful fishes just like the Green Neon are found in giant schools in nature, and should be kept as such in an aquarium. There are now two color morphs known. A “dark” form containing 12 oblique lines across the body, and a “light” form that shows diffused dotted lines. It is my belief that these occur together as it seems we were sent such.

Carnegiella marthae

I was unable to determine the river source, or the correct identification, for what is being imported as Farlowella acus “Twig Catfish”. It is likely that our shippers are actually sending Farlowella vittata, as F. acus is now considerably endangered and rare in the hobby. Sadly, this is probably due to overfishing for the aquarium trade. In my research, I found several species of Aguja (as the people of Venezuela know them), but have been unable to properly identify the truly unique “stick” like fish we have. The Twig Cat is a great algae eater that predominately feeds on diatomaceous (brown) algae. Males of this species can reach around 8” while the female probably stays a little smaller. It is essential for the Twig Cat to have pieces of root wood in their aquarium. Without the wood the fish do not do well and seem to perish. Like myself, these fish know how to appreciate fine facial hair and grow a long “mustache” that is known as odontodes and is used to coax a female into breeding. See ladies, even fish know a 'stache is the only way to go ;)

Farlowella acus

Hanging above fallen leaf litter among the roots of trees in the Rio Negro to the Rio Orinoco is Biotodoma wavrini “Orinoco Eartheater”. The original erection of the genus was derived from the Greek words “biotos” for “life” and “domos” for “house” and was the opinion of the original author because he thought these fishes were mouth brooders. Today, we now know that Biotodoma actually lays specialized eggs that will attach themselves onto the substrate with a unique apparatus. This very peaceful cichlid only grows to only about 4” and does not seem to harm even the smallest tank-mates. These elegant cichlids rather spend their time digging in the substrate in search of microorganisms much like their cousins of the Geophagus complex. Despite their unique diet, you should continue to feed frozen bloodworms, daphnia, and small amounts of flake. I always found that they were very fond of Omega One’s Super Cichlid Pellets and highly recommend them for any eartheater.

Biotodoma wavrini

All of these fish stay fairly small. Because of this, you could easily get away with a 40 breeder, or a tank of a similar footprint. I would suggest keeping the tank rather acidic. It doesn’t have to be battery acid, but a good basis would be in the low 6.0’s. I would put a couple of pieces of driftwoods in the corner with maybe a nice piece of slate near the middle to encourage the Biotodoma to spawn. The filter should be oversized, but with minimum flow near the surface as to not to disturb the hatchets too terribly.

One more newsletter is under us and another week has passed. At the end of this week, we will bring more Asian fish to our list, so don’t miss out! If you have any questions or concerns please contact me. Until next week!

Anthony Perry

Sales Manager