Backwater in the rainforest, Asahan River, Sumatra, Indonesia

87th place in Biotope Aquarium Design Contest 2018

russia Russia. Varvara Kozmenko

Volume: 70 L
Dimensions: 67х32х25 cm
List of fishes: Betta rubra
List of plants: N/A
Description of decorations: Beige sand, roots of aronia and birch, leaves, small twigs.
Description of equipment: ASAP 300 AquaEl filter, AquaEl LEDDY SMART 2 lamp 6W, heater EASYHEATER 25W.
Water parameters: 25°C, рН is 6.0, КН is 1, GH is 4.


Description of the area surrounding the biotope: The region is isolated from the rest of the island by the Barisan Ridge, which is an integral part of the belt of active volcanoes that stretches in the marginal zone of the Pacific Ocean and is called the “Pacific Ring of Fire”. There is increased seismic activity (earthquakes reach 7-9 points) here, and a half dozen of active volcanoes, including the highest point of Sumatra: Kerinci volcano (3800 m). The region is considered to be a separate area of ​​ichthyofauna due to the high proportion of endemic species found only there. The tropical rain forest surrounds the river, its bottom is covered with a layer of fallen leaves and branches, the water surface is broken with numerous tree roots. The Asahan River flows from the largest lake in Sumatra: Lake Toba, which appeared many millions of years ago in the crater of an extinct volcano. The backwater shown in this aquarium is a home for the couple of Betta rubra. This species was described quite a long time ago, but due to local conflicts between the government and local freedom fighters, the territory in which this species lives is closed to the public, and it was impossible to catch the fishes. In December 2004, a huge tsunami caused by an earthquake in the Indian Ocean hit this part of the island and killed 230,000 people in this province alone. This destructive act of nature, which brought so much misfortune, ultimately helped to conclude a peace agreement between the parties. The area was opened to the public, and since 2007, Betta rubra has been on sale and in amateur aquaria around the world. B. rubra bears its fry in its mouth.

Description of the underwater landscape of the biotope: The bottom of the reservoir consists of sand mixed with earth and is covered with a layer of leaves, branches and other plant debris. The roots of coastal trees and shrubs descend into the water. Due to the shade there is practically no aquatic plants in it. The water is brownish, slightly turbid. There is almost no flow there.

Description of the parameters of the habitat: The water is brownish, slightly turbid. There is almos no flow there. The water is warm, sour and soft: 23-27°C, pH is 5-6.5, КН is 0-1, GH is 1-4. The seasonal flood, which occurs from October to April, softens the water of the river basin even more, and the pH also shifts to the acidic side, which is as a signal for spawning for the fishes.

List of fishes and invertebrates occurring in the nature biotope: Parosphromenus sumatranus, Trichogaster leerii, Sphaerichthys osphromenoides, Helostoma temminkii, Nandus nebulosus, Chaca bankanensis, Pseudeutropeus brachypopterus, P.moolenburghae, Mystus bimaculatus, Pseudomystus leiacanthus, Kryptopterus macrocephalus, Silurichthys indragirensis, Puntius johorensis, Parachela oxygastroides, Rasbora cephalotaenia, Osteochilus spilurus.

List of plants found in the nature biotope: Microsorum pteropus, Hygrophila corymbosa, Cryptocoryne cordata, Riccia fluitans, Vesicularia, Nymphaea.

Threats to the ecology: The ecology of Lake Toba, and, consequently, the rivers flowing from it, has recently got worse significantly. The reason for this is the economic activity of the islanders without the use of sewage treatment plants. Also in certain months the lake turnes green, which is caused by the presence in its waters of a large amount of nitrogen and phosphorus. Given the large number of endemic species in the region, every effort should be made to conserve them.

Sources of information:

Comments of the members of the jury of Biotope Aquarium Design Contest 2018