Setting Up a Southeast Asian River Biotope Aquarium
South East Asia includes the mainland and the islands of Sumatra, Borneo, and Java. In ancient times, these areas were connected by a vast river system. Today, this region is characterized by lush rainforests where land water flows into numerous tributaries. The rivers here have very little current, creating a slow-moving environment with dense, decaying vegetation. Bamboo and ferns thrive both above and below the waterline. The natural substrate and rocks have a deep red hue due to high iron concentrations, although the overall mineral content is low.
The rotting plant matter in these rivers makes the water acidic. For your biotope, aim to maintain a pH level between 6.0 and 6.5. The water hardness should be between 2 and 8 degrees of hardness (DH), and the water temperature typically ranges from 26 to 29°C (78.8 to 84.2°F). These conditions should be replicated in your tank.
Some areas might have low concentrations of salt, which can be beneficial to the fish if added in small amounts without harming the plants. As the natural environment includes various shallow river tributaries, tank depth is less critical compared to tank length.
Setting up the Tank
For this biotope, tank length is more important than depth. To recreate the shallow river environment effectively, I recommend a tank that is 48 inches long, 12 inches wide, and 15 inches high (122 cm x 30 cm x 38 cm). This setup will mimic a long, shallow river. If space is limited, a 36-inch tank (91 cm) can be used, but keep in mind that some fish species in this setup can grow quite large. The substrate should resemble the deep red iron-rich soil of the natural habitat, so using rich red laterite is ideal. This will also benefit the plant life. On top of this, add fine red gravel or sand, and consider separating areas of sand and gravel for visual interest. Another option is Seachem Fluorite, a red clay gravel that promotes plant growth. Include some bogwood to simulate tree roots, but avoid overusing it as it can detract from the effect. Scatter small pebbles and rocks randomly, ensuring they are inert to prevent any reactions with the acidic water. The substrate should be slightly higher at the back of the tank to create a sloping bank effect and to allow detritus to accumulate at the front for easier siphoning. This completes the hardscaping; next, focus on selecting and arranging the plants.
Plants for the Biotope
Recommended plants for this setup include Cryptocoryne Wendii, Cryptocoryne Nevilli, and Hygrophila Polysperma. Some aquarists also add Vallisneria to provide a mid-ground effect with its long, upward-floating leaves. However, Vallisneria typically thrives in neutral to slightly alkaline conditions, though it may still grow in an acidic environment. If you wish, you can experiment with a few plants to see how they adapt.
For Cryptocoryne species, it's best to introduce them after the tank has been running for 2-3 months. These plants are sensitive to new setups and may experience "crypt meltdown," where the leaves die off. However, they usually recover and grow back if left undisturbed.
Onion plants can also be suitable; just make sure to keep the crown of the bulb above the substrate. Bamboo plants are another good choice. If your tank has an open top, allowing some bamboo shoots to extend above the water can create a striking visual effect.
Suitable Fish
Suitable fish for this biotope include most Loaches, Barbs, Danios, Red tail sharks, Bala sharks, and small Asian catfish. Ensure the tank size matches the adult size of the fish or be ready to upgrade to a larger tank as they grow. Bala sharks and Clown loaches, for example, will outgrow a 36-inch (91 cm) or 48-inch (122 cm) tank, so research their adult sizes before purchasing. A stunning biotope can also be achieved with just a shoal of Green tiger barbs.
Lighting for the Tank
Provide adequate lighting to promote plant growth, but avoid excessive lighting, which can diminish the natural look you aim to create. If lighting seems insufficient, consider adding a CO2 system to compensate, but allow the plants to settle in before investing in this additional equipment.
Filtration
For any aquarium setup, the filtration system must be adequate for the livestock. However, you want to avoid strong currents that could disrupt the natural look of your biotope. If using an external filter, add a spray bar to spread the flow from the outlet pipe. Position the spray bar to direct the current toward the back glass to minimize flow further. For internal filters, you might find spray bars designed for popular models, or use a wide outlet nozzle to reduce water flow.
If the gentle flow isn't enough to maintain adequate oxygen levels, you might need to add extra aeration. A steady stream of bubbles from an air line, placed discreetly in the corner of the tank, should not be too noticeable.