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t is the month of October 2018 and the topic is a small member of the Loricariidae family and one of the most stunning discoveries of the last 14 years namely the "Green Oto" Hisonotus aky. This fish caused quite a stir in the hobby when first described and all these years later it has now been bred in the hobby.

Hisonotus aky

Hisonotus aky (Azpelicueta, Casciotta, Almirón & Körber, 2004) was originally described in Epactionotus Reis & Schaefer, 1998 because of its supposed possession of three synapomorphies proposed for that genus: neural spine of seventh vertebra not contacting nuchal plate dorsally (contacting unpaired predorsal plates), first dorsal proximal radial contacting the eighth vertebral centrum, and absence of an expanded fleshy flap on the dorsal surface of the first pelvic-fin ray in males. Also, Hisonotus aky possesses one of the additional diagnostic characters of Epactionotus: longitudinal light stripes on dorsal surface of head. However, the examination of type specimens of Epactionotus aky indicates the absence of most diagnostic features for the genus.

Hisonotus aky - three day old fry

This species has been bred by English aquarist Paul Dixon from the Bolton Museum, England and is shown above.

According to Evers et al, they are only found in a small area in the Rio Uruguay drainage in the Fortaleza Creek, close to the city of Paraiso.

A very unique species, in that it can be easily recognised by its overall green body colour, although freshly imported specimens are often olive coloured and do not show the bright metallic green colouring until well settled.

Green Oto

Epactionotus aky

Hypoptopomatinae

South America: Argentina, Yabotí-Guazú basin, Uruguay River system, Misiones. Type locality: Argentina, Misiones, Río Uruguay basin, Arroyo Garibaldi (26º38'46.1"S, 53º59'55"W).

4.5cm. (1¾ins)

18-24°c (63-75°f.)

The following summary is from AZPELLICUETA et al (2004). Epactionotus (Hisonotus) aky is diagnosed by the following combination of characters: 1) 21 to 23 lateral plates; 2) light stripes extended from snout tip to supraoccipital level; 3) caudal fin with dark vertical stripes; 4) ventral surface of body completely covered by small platelets; 5) 1-4 feeble serrae on distal portion of pectoral spine posterior margin.

Peaceful fish with other companions who like water movement in the aquaria.They rest on aquatic vegetation in the aquarium and the less light in the tank the darker they become. Provide a current in your tank for this species as they come from swift flowing waters. A sandy substrate is best with smooth rocks and pieces of bogwood, with thickets of broad-leaved plants such as Amazon swords.

They lay their eggs on plant leaves.

Will feed on flake, algae, tablet foods, algae wafers and insect based foods.

Hisnotus: Greek, isos = equal + Greek, noton = back.
aky: aky (language: guaraní) = green.

Photo Credits

Top: © Ingo Seidel @

Bottom: © Paul Dixon @