Small affluent to Rio Paragua, Noel Kempff Mercado National Park, Bolivia

_ place in Biotope Aquarium Design Contest 2019

Volume: 345 L
Dimensions: 180x60x32 cm
List of fishes: Apistogramma trifasciata, Corydoras sterbai, Aphyocharax rathbuni
List of plants: Eichhornia diversifolia, Hydrocotyle leucocephala (emersed mostly)
Description of decorations: Roots, branches and twigs covers a sandy substrate (0,4-1,2mm). Mix of peat, leaves, bark and small branches lays in the parts of tank with small current. Few bigger roundish rocks, and some gravel occurs in the main stream bed (place with bigger current on the right)
Description of equipment: Eheim 2228 external filter, Eheim skim 350, Rossmont mover M4600 circulation pump, 2 x SANRISE F002 48W lamps (set on 10%), 8x IKEA JANSJÖ 2W lamps
Water parameters: Temperature varies from 21 to 28 degrees Celsius (depends on time of the year) but for most of it stays in about 23-24 degrees.
KH 1, GH 2, pH 6,5-6,8, conductivity 50-100 µS/cm (depends on simulating the rainy and dry season)
Additional info: Tank is balanced with flora and fauna numbers to prevent of nitrates and phosphates build up, therefore water changes are needed only to simulate rainy season. The scheme is 3x 30% w/c once a week, and then 4 months without w/c. Main lightning is ment to create “light background” and eight smaller lamps imitates sun beams.


Description of the area surrounding the biotope: Noel Kempff Mercado National Park was created in 1979 (previously named Huanchaca National Park) and is located in zone where Amazonian forest integrates with the dry forest and savanna habitats. Habitat types of the region can be grouped into five different ecosystems: upland evergreen forest, deciduous forest, upland cerrado savanna, savanna wetlands and forest wetlands. The savanna wetlands are linked to the famous Pantanal, so there are similarities in flora and fauna in these regions. Area of 15 838 square kilometers of park provides place for flora and fauna richness that is extremally big and consists almost 2700 plant, 600 bird, 130 mammals, 130 reptiles and 250 fish species. Richness in fish species of area represents 60% of the whole Amazonian ichthyofauna known from Bolivia. The Itenez basin (Rio Itenez is the north border of park) is the only major river system that originates on the Brazilian Shield, causing it to be dramatically different from other rivers of Bolivia in the physical and chemical characteristics of its waters. Some 65 fish species of the Itenez basin either are endemic or have relatively restricted distributions. The high overall diversity reflects the variety of aquatic systems in the park, ranging from small clear water streams to large black water lakes and rivers. Savanna and forest floodplains offers many specialized habitats. Some watersheds of park (Rio Verde, Rio Paucerna) are isolated from the main Itenez drainage by waterfalls and rapids, so there are places when endemic species occur greatly. This isolation may date back more than 6 milion years.
The principal rivers found in the park are part of Rio Itenez (Guapore) basin, including sub-basins of the Rio Verde, Paucerna and Paragua. Lacustrine systems include lakes derived from rivers, as well as subsidence lakes. Palustrine wetlands are found within the Rio Paragua basin, where they form extensive areas of seasonally flooded forests and savanna wetlands. The largest river in the area is Rio Itenez (northern and north-east border of park). Another important river is the Paragua, lefthand tributary to Itenez, that flows from south to north (western border of the park). These two rivers are considered to be “atypical” black water rivers. Altough the dark coloration, they have almost neutral pH and are more rich in chemicals contrentations than the formally classified Amazonian black water rivers. Black water rivers in park are formed by intensive biodegradation of plant matter in savanna wetlands, which process is responsible for the tannin richness in water. Two other main rivers in park are Rio Paucerna and Rio Verde. Both river systems are characterized by having clear to slightly black water, rapid stream flow, and well defined river channels.
Rio Paragua has the main channel that vary between 10 and 30m in width, and depth up to 10m. The river banks vary in height but for the most part are abrupt. Beaches are not commonly observed and the bottom is less sandy compared to the Rio Itenez due to higher content of loam and decaying plant matter.
Small black water streams that are tributaries of the Paragua river (represented in my aquarium) traverse the lowland plain situated west and south of the Huanchaca plateau. Stream dimensions are small with a maximum width up to 2m, but incease in size considerably during the rainy season. Stream banks vary in height but generally are abrupt; bottoms are either sandy or loamy. Aquatic vegetation varies — streams in the forest shade usually have few aquatic plants, but in clearings streams are dominated by floating and emergent vegetation.

Description of the underwater landscape of the biotope: Almost 2m wide, and 30cm shallow (in dry season) stream tributary to Rio Paragua. “Atypical” blackwater (according to Sioli definition) with water parameters closer to classical clearwater streams. Section with abrupt, eroded bank on the left side, under the roots of nearby tree. Roots slows water current, and it leads to create nice habitat for smaller fish like Apistogramma trifasciata and Aphyocharax rathbuni. Hydrocotyle leucocephala, growing emersed on bank and roots, keep the light low; small twigs, bark, leaves and other sediments gives good shelter and spawning area. Slower current creates a place with abundand food source, which is perfect for fry to raise. In front of bigger wood piece, that lay on the right part of stream section, some Eichhornia diversifolia grows in the area, where sunrays reaches bottom better. Stronger current occurs only in narrow, clear part of stream. Some gravel, and few roundish rocks lays there. This is the spot where mentioned fish swim only while migrating into planted area, or up/down the stream, and where Corydoras sterbai swim while searching for food in the stream bottom. Water is well oxygenated and a little turbid (much more in the rainy season).

Description of the parameters of the habitat: Water parameters varies depends on time of the year, and water is “coloured” with tannins, soft and slightly acidic with parameters: pH 6,3-6,8; hardness 1 odH; electrical conductivity 15-100 µS/cm (depends on the rainy and dry season), temperature 22-28 oC

List of fishes and invertebrates occurring in the nature biotope: Aphyocharax sp., Acestrorhynchus sp., Hemigrammus sp., Hyphessobrycon sp., Moenkhausia sp., Nannostomus sp., Pyrrhulina sp., Otocinclus sp., Rinelocaria sp., Apistogramma sp. Laetacara sp., Mesonauta sp.

List of plants found in the nature biotope: Echinodorus sp., Ludwigia sp., Cabomba furcata, Myriophyllum sp., Hydrocotyle sp., Salvinia auriculata, Eichhornia sp., Urticularia sp., Cyperus sp., Xyris sp., Eriocaulon sp.

Threats to the ecology: Like everywhere on Earth main threat is human. Exploring of natural resources, cutting trees, planting soy and other crops. Fortunatelly the Bolivian government reacts very good in the area of wetlands, and National Park preserves the natural beauty of the area.
Global problem that affects park is a phenomenon called El Nino. This causes draughts, and therefore creates problems in wetland areas. Also high level of CO2 in atmosphere is predicted to reverse the expansion of tropical rainforests. This process can have impact on vulnerability of rainforests to sustain while draugths.

Sources of information:
— Preliminary study of fish fauna and aquatic habitats in the Lower Paraguá River, Santa Cruz, Bolivia (
— Rapid Assessment Program 10 “A biological assessment of Parque Nacional Noel Kempff Mercado,Bolivia” (

Comments of the members of the jury of Biotope Aquarium Design Contest 2019