Shallow Backwater Pool, Río San José, Horquetas, Costa Rica

Aquarium information

Aquarium description

Set-up date

February, 2025

Aquarium decoration

The aquarium’s decoration was carefully designed to authentically replicate the natural environment of the San José River’s side arm. A warm, brown-colored sand was selected for the entire substrate, representing the soft riverbed found in this habitat. Along the edges, rounded stones were arranged to recreate the feeling of a gently sloping riverbank. Towering above these, intricate root structures extend across the aquarium, faithfully mimicking the characteristic roots of the Sotacaballo tree (Zygia longifolia).

Over time, these roots have naturally become covered with algae, a result of the carefully controlled photoperiod provided by Kessil lighting and the natural sunlight that streams through a nearby window. Watching the light beams penetrate the water, just as they would through the forest canopy, creates a mesmerizing play of shadows and bright spots, bringing the scene to life.

To further enhance the authenticity, I regularly add botanicals during each maintenance session – small branches, fragments of driftwood, and dried leaves. These elements slowly decompose, releasing tannins and forming biofilm and detritus over the roots, just as they would in the wild. This creates not only a visually accurate environment but also a functional habitat that supports the natural behaviors of the fish.

The substrate itself is deliberately kept imperfect. Rather than maintaining a pristine, flat sandbed, small stones, twigs, and scattered leaves are left in place to simulate the complex textures of a real riverbed. This adds depth and realism to the scene, making every corner of the aquarium feel alive and dynamic.

Observing the fish in this setup reveals fascinating natural behaviors. Some species confidently swim near the surface and in open areas, feeding on the algae and microorganisms growing on the roots. Others, more cautious, remain hidden in the dark hollows beneath the roots. Over time, a beautiful interaction unfolds – bolder fish seem to reassure the shy ones, encouraging them to leave the safety of their shelters and venture out into the filtered light.

It’s captivating to watch as the community finds balance, with each species playing its role. This dynamic interplay, the contrast between light and shadow, and the movement between hiding and exploring perfectly capture the essence of the natural biotope. Standing in front of the aquarium, you don’t just see an aquarium – you feel transported to that quiet, hidden corner of the San José River.

Aquarium equipment

The aquarium uses a sump filtration system with three compartments: the first contains filter pads and sponges; the second holds biological media; and the third houses the Eheim Jäger 300W heater and the return pump. The system is supported by a return pump Jebao DCP-3500 liters and two Kessil A360X lamps for lighting.

Fish care

Fish care in this biotope centers on replicating natural feeding behaviors and ensuring all species receive adequate nutrition. Poecilia gillii are active swimmers that occupy surface and midwater zones, so they are offered floating or slow-sinking pellets, which allow them to feed comfortably in their preferred areas.

Immediately afterward, Cribroheros rostratus are fed sinking pellets and frozen foods. Despite their larger size, these cichlids are notably timid and exhibit distinct substrate-sifting (“earth-eater”) behavior. They prefer to feed near the bottom, methodically filtering sand and detritus in search of food. To accommodate this, fast-sinking foods are provided to ensure they reach the substrate before being intercepted by the quicker poeciliids.

The aquarium layout supports this behavior by maintaining open sandy areas beneath the root structures. These hollows act as visual barriers and refuges while allowing Cribroheros rostratus full access to the bottom, where they can forage naturally. This thoughtful feeding strategy and habitat design allow both surface-active species and shy bottom-dwellers to coexist peacefully, without competition or stress.

Fish list:

• Criboheros rostratus (Cichlidae)
• Alfaro cultratus (Poeciliidae)
• Poecilia gillii (Poeciliidae)

Plant care

Water care

Water care in this biotope aquarium focuses on maintaining stable conditions that replicate the natural environment while ensuring the health of the fish and plants. The primary routine involves performing weekly water changes to remove accumulated waste and replenish essential minerals. Additionally, due to the high water temperatures that promote significant evaporation, it is important to regularly top off the tank with dechlorinated or conditioned freshwater to maintain stable water levels and prevent fluctuations in water chemistry.

Regular inspection and maintenance of the sump system are also essential. The mechanical filtration compartment should be cleaned frequently to remove trapped debris, ensuring that water flow remains unobstructed. It is equally important to check that the return pump is functioning properly and that no blockages or airlocks are affecting the circulation.

Dimensions

Length

120 cm

Depth

70 cm

High

50 cm

Volume

420 L