The Slaty leaf fish from northeast India that has been showing up in the aquarium trade recently has been formally described as Nandus andrewi.
Heok Hee Ng and Zeehan Jaafar of the National University of Singapore described the new species in a recent issue of the journal Zootaxa.
The new species comes from the Ichamati River in the border region between India and Bangladesh, and is easily distinguished from all other members of the genus by its slatey colour (all other Nandus are a mottled brown).
It further differs from the other Indian Nandus species, N. nandus, in having a more slender body and shorter pelvic fins.
The species is named after Andrew Arunava Rao of Malabar Tropicals, who first exported this fish and made the authors aware of its existence. More information on this species can be found in the Interesting Imports article here: Matt Clarke (2007) - Nandus andrewi, Slaty leaf fish, Interesting Imports, Practical Fishkeeping.
For more information, see the paper: Ng, HH and Z Jaafar (2008) A new species of leaf fish, Nandus andrewi (Teleostei: Perciformes: Nandidae) from northeastern India. Zootaxa 1731, pp. 24-32.