#1150 Floodplain-sungai kolok (Narathiwat) -Thailand

Biotope Information

Introduction Betta imbellis is a freshwater species native to Southeast Asia, commonly found in shallow, acidic water bodies rich in organic matter. Its labyrinth organ allows it to breathe air in waters with low dissolved oxygen, giving it an advantage in tropical lentic systems. In this context, the Ban Buketa region constitutes an ideal ecological microcosm. This study explores its biophysical conditions, with an emphasis on seasonal tannin fluctuations and their impact on the habitat. Location and Hydrological Regime Ban Buketa (Waeng, Narathiwat) is located at 5°50'48"N 101°53'34"E, in the Sungai Kolok River basin. During the rainy season (May–November), the area becomes a floodplain with shallow (<1 m) temporary water bodies connected by natural channels and peatland areas. Physicochemical parameters and climate pH: 5.5–7.0 Temperature: 24–28°C Dissolved oxygen: low (<3 mg/L) Conductivity: During the dry season or clear water: 10–20 µS/cm During the rainy season: up to 60 µS/cm Turbidity: variable depending on vegetation cover and precipitation Typical environments: shallow, slow-moving, or stagnant waters with floating/submerged vegetation Seasonal variation in tannins During the rainy season, the runoff of leaf litter, decomposing roots, and plant debris produces a significant release of tannins, which tint the water with amber-brown tones. This black water is typical of tropical peatland ecosystems. During periods of maximum flooding, the tannin concentration is moderate due to the high volume of water that dilutes the organic compounds. During the post-monsoon recession phase, the water level drops and organic matter concentrates, resulting in higher levels of tannins, increased acidity, and reduced optical transparency. These conditions reduce light penetration, alter the structure of the primary community, and favor species adapted to dark and acidic environments, such as Betta imbellis. Dominant Aquatic Vegetation The aquatic flora includes: Neptunia oleracea Limnocharis flava Barclaya longifolia Murdannia keisak: emergent herbaceous plant at the edges of ponds Limnophila spp.: submerged plants with structural and oxygenating value These species contribute to nutrient cycling, litter retention, and provide physical support for bubble nests. Associated Aquatic Fauna Boraras maculata: small cyprinid, coexisting with Betta imbellis. Limnopilos naiyanetri: a freshwater crab that inhabits roots and detritus, a bioindicator of structurally complex habitats. Other anabantoids such as Betta pi, Trichopsis vitata, and Trichopsis pumilla, macroinvertebrates (Caridina spp., dipteran larvae), and larval amphibians. Discussion Seasonal tannin variations are a critical ecological component. They affect water chemistry, reduce the photosynthetic rate at deeper levels, and modify trophic relationships. Betta imbellis, by building nests at the surface and feeding on invertebrates, is perfectly adapted to this fluctuating environment. The presence of Limnopilos naiyanetri and Boraras maculata suggests structural stability and diversity of microbenthic niches. Conclusion Ban Buketa represents a highly relevant tropical floodplain model from an ichthyological perspective. The seasonal influence of tannins on water chemistry and habitat structure reinforces the need to conserve these types of aquatic systems. Betta imbellis and its associated fauna find a functional, highly specialized refuge here. References Ladiges W. (1975). Betta imbellis nov. spec., taxonomic description. DATZ 28(8): 262–264. FishBase (2025). Betta imbellis, environmental parameters pH, temperature, hardness. seriouslyfish.com+13fishbase.se+13aka.org+13de.wikipedia.org+1roloffia.com+1 Fishipedia (2023). Ecological data of flow and habitat environment BIOTOPE AQUARIUM FOR BETTA IMBELLIS Inspiration and Hardscape After gathering information, we applied everything we collected to replicate this biotope as faithfully as possible. We were inspired by images from great books like *Labyrinth Fish World* by Hors Linke and by videos that show even the smallest details, such as those by Rodrigo Silva. The habitat to be recreated is a flooded area dominated by marginal, marsh, and floating plants, as well as large clumps of reeds and their corresponding organic remains. Therefore, the main material for this project is reeds, which are the primary element of the scene, and we incorporated a high amount of organic matter. This project does not include rocks since the location is a flooded area where they are barely visible. Once the structure was built and the botanicals added, I incorporated a small layer of clay substrate and a thin layer of neutral sand, which will serve as a base for the plants selected for the project. We added 12 plants of Murdania keisak, a very common plant in these environments and one that defines the project. As floating plants, we added Salviani and Lemna minor. Given this biotope, we decided to focus on a rainy season, where we find those characteristic whitish waters and soils full of leaves and organic matter. This is how we managed to recreate the perfect environment for the fauna that will be introduced later. Fauna Boraras maculata Limnopilos naiyanetri Betta imbellis Tank The selected tank is a shallow 70x35x20 cm tank. Equipment Filter: Sicce whale 120 Biological filtration: Neo media pure Lighting: Chihiros b series 60cm WATER PARAMETERS pH: 6.2-6.5 GH: 0.3 KH: 0.3 TEMP: 23/24ºC The splendens complex: taxonomy, ecology, and adaptations The Betta splendens complex represents a closely related group of anabantoid fish from Southeast Asia, known for their bubble nest breeding behavior and their ability to breathe atmospheric air. Although the domesticated form of Betta splendens is widely known due to its popularity in aquariums, its wild counterparts comprise several species with distinct ecological and morphological characteristics. This article describes the main species of the complex, their natural habitat, reproductive behavior, and geographic distribution. Taxonomy and members of the complex The Betta splendens complex includes at least six closely related species, all belonging to the subgenus Betta. The most representative are: Betta splendens (wild) – Central Thailand Betta imbellis – Southern Thailand, Malaysia, Indonesia Betta smaragdina – Northeastern Thailand and Laos Betta mahachaiensis – Coastal areas of central Thailand, near Bangkok Betta siamorientalis – Eastern Thailand Betta stiktos – Southern Cambodia and Laos These species share general morphology and reproductive behavior, but differ in color patterns, body proportions, specific habitat, and geographic distribution. Natural habitat Members of the complex inhabit shallow freshwater bodies, frequently in seasonally flooded areas. Typical environments include rice paddies, peat bogs, canals, roadside ditches, and marshy areas with dense vegetation. Common physicochemical conditions: pH: 5.5–7.5 Temperature: 24–30 °C Hardness: soft to moderate Conductivity: 10–100 µS/cm Dissolved oxygen: low The water in these habitats is often tinged brown by tannins, with a substrate of leaf litter and soft sediments. Species of the splendens complex are adapted to these conditions thanks to their labyrinth organ, which allows them to breathe atmospheric oxygen. Reproduction All species in the complex reproduce by bubble nesting. The male builds a nest on the surface, courts the female, and collects the eggs after they are laid. During incubation, the male guards and repairs the nest. The fry hatch 24 to 48 hours later and become free-swimming within 3 to 5 days. Diet They are microcarnivores, feeding in the wild on insect larvae, small crustaceans, zooplankton, and other aquatic invertebrates. In laboratory or aquarium conditions, they accept live, frozen, or protein-rich microgranulated foods. Conservation Status Many wild populations are threatened by: Habitat loss Pollution Introduction of domestic varieties and hybridization Species such as Betta mahachaiensis and Betta stiktos have very restricted distributions and require monitoring for conservation. Conclusion The wild Betta splendens complex is a fascinating model of ecological and reproductive diversification in tropical environments. Understanding it is key both for conservation in its natural habitat and for understanding the evolution of domesticated forms.