Type locality is ‘Laguna Larga, 6.5339°N, 67.4150°W, Río Cinaruco, Apure, Venezuela’ but this species known to have a wider distribution within both black and clear water tributary systems of the río Orinoco throughout the Venezuelan Llanos including the ríos Apure, Cinaruco, Capanaparo, Aguaro and Guariquito.
It also occurs in the río Caura on the Guyana Shield plus the Ventauri and Mavaca drainages in the middle and upper Orinoco where it’s also known from some white water, referring to turbidity rather than turbulence, habitats.
To the north its distribution appears limited by the Las Majaguas dam on the Río Cojedes, a tributary of the Apure where a probable introduced population inhabits the reservoir formed by the dam.
To the south it’s found as far as the Río Casiquiare, close to the headwaters of the rio Negro (Brazil).
The Llanos is a vast, highly biodiverse system of tropical savannah grasslands, seasonally-flooded plains and forests covering an area measuring almost 600,000 square kilometers in Venezuela and Colombia.
It’s located to the north and west of the Río Orinoco and drained by many of that river‘s tributaries.
There are well-defined annual weather patterns with distinct wet and dry seasons and year-round high temperatures.
G. abalios occurs predominantly in lowland floodplain rivers where it’s known to enter inundated zones during the rainy season. At this time many rivers break their banks forming a complex series of interconnected channels and lagoons.
At other times of year it mostly inhabits clear, black waters typfied by low pH, negligible conductivity and little suspended sediment, and is more commonly found in still lagoons rather than river channels.
Substrates are generally soft, bare sand or mud, and depending on locality other habitat features can include scattered rocks, submerged tree roots, branches and leaf litter.
It’s often found living sympatrically with G. dicrozoster, even occupying the same habitat at some localities, though the two practice different breeding strategies with the latter a larvophilous mouthbrooder.
Other fishes occurring in the region and available in the aquarium trade include Corydoras delphax, Platydoras costatus, Baryancistrus beggini, Hypancistrus inspector, Panqolus maccus, Panaque nigrolineatus, Hemigrammus rhodostomus, H. stictus, Hyphessobrycon sweglesi, Paracheirodon axelrodi, Pristella maxillaris, Copella nattereri, Biotodoma wavrini, Heros severus, Mesonauta insignis, Satanoperca daemon and Uaru fernandezyepezi.