How to Aquascape for Exclamation Point Rasboras: Dense Nano Jungle

Exclamation point rasboras — Boraras brigittae — are among the smallest and most visually striking fish available to aquarists, reaching barely 1.5–2 cm and displaying intense red colouration with a bold black spot that earns them their common name. Their scale demands a very specific aquascape approach: everything in the tank must be proportioned to the fish’s tiny size, or they vanish visually against oversized plants and hardscape. Designing an aquascape for exclamation point rasboras in a nano tank is an exercise in scale and intimacy that produces a result unlike any other planted tank style. Gensou Aquascaping at 5 Everton Park, Singapore, keeps and breeds Boraras species regularly and finds them one of the most rewarding nano fish in the hobby.

Tank Size: Small Means Proportional, Not Minimal

A 20–45 litre tank is ideal. Larger tanks technically work but dilute the visual impact of such small fish — a 12-litre tank feels cramped, but a 150-litre tank makes a school of 20 rasboras seem almost invisible. The 30-litre ADA Cube Garden 30C (30 × 30 × 30 cm) and similar dimensions have become a popular format precisely because they suit nano fish display so well. At this scale, plants fill the frame quickly, the fish are always close to the viewer, and every detail of their colouration is visible. Singapore’s HDB-friendly footprint of a 30-litre cube — under 30 cm wide — also makes it practical for desk or shelf placement.

Plant Scale: The Most Critical Design Decision

Large-leaved plants dwarf 2-cm fish entirely. Anubias barteri leaves are bigger than the fish. Even medium stem plants like Rotala rotundifolia at full height can overwhelm a school of Boraras brigittae. Choose plants with fine leaves and small growth habit throughout. Foreground: Hemianthus callitrichoides ‘Cuba’ (HC) carpet, 2–3 mm leaf, or Eleocharis parvula (dwarf hairgrass). Midground: Micranthemum monte carlo, Staurogyne repens, or small Cryptocoryne parva. Background: Rotala rotundifolia kept trimmed short (5–8 cm), or Murdannia keisak for fine-textured growth. Mosses — Java moss, Peacock moss — tied to miniature driftwood or small stones add fine texture at any depth.

Blackwater or Clear Water?

Boraras brigittae originates from the blackwater peat swamp forests of Borneo, and in their natural habitat, pH is 4.0–5.5 and water is tea-coloured. In the aquarium, they tolerate a broader range but genuinely colour up better and behave more confidently in soft, slightly acidic water (pH 5.5–6.5, GH 0–4). A light tannin addition — two or three Indian almond leaves per 30 litres — provides mild tannin staining and pH buffering without creating full blackwater conditions. This slight amber tint also photographs beautifully and enhances the fish’s red colouration by contrast. Singapore’s soft tap water is a good starting point, requiring only dechlorination and a small catappa leaf supplement.

Hardscape at Nano Scale

Small stones and miniature driftwood pieces are proportionately correct for a Boraras tank. Look for stones 3–8 cm in size rather than the 15–30 cm boulders used in larger aquascapes. Spiderwood’s fine branching structure provides scale-appropriate visual complexity — a single 20-cm piece of spiderwood with multiple fine branches creates the impression of a dense root system without filling the entire tank. Collect small stones from landscaping suppliers or aquarium shops; they’re often sold by weight at $2–$5 per kg and offer good variety in a small quantity.

Flow and Filtration for Tiny Fish

Small sponge filters and nano internal filters are the appropriate filtration choice. Canister filters with strong return flow create currents that are too strong for 2-cm fish — Boraras brigittae will be blown around and exhaust themselves maintaining position. Target a gentle turnover of 3–5 times tank volume per hour, with the outflow directed against the side glass to diffuse current rather than creating a direct jet into the open water column. A Matten filter or a small ATI Hydro sponge filter at $10–$18 provides gentle biological and mechanical filtration appropriate for a nano setup.

Stocking Numbers and Behaviour

Unlike larger fish species, exclamation point rasboras display their best behaviour in larger groups. Twenty to thirty fish in a 30-litre tank is not overstocking — it’s appropriate for the display effect. At this density, the males colour up more intensely as they compete for females’ attention, the school moves as a shifting, coordinated unit, and the visual impact is that of a cloud of red and black moving through dense plant growth. Feed micro pellets, crushed flake, and live or frozen micro foods: vinegar eels, micro worms, and baby brine shrimp nauplii. Avoid any food item larger than 0.5 mm — the fish genuinely cannot fit larger particles in their mouths.

Long-Term Nano Tank Stability

Small tanks are inherently less stable than large ones — parameters shift faster, temperature fluctuates more, and a single missed water change can spike ammonia in a heavily stocked nano. Weekly 20–30% water changes using pre-treated, temperature-matched water are the foundation of stability. Singapore’s warm ambient temperature makes temperature matching easy; simply leave the change water bucket out for 30 minutes before adding. At 26–28°C ambient and with appropriate soft-water parameters maintained, Boraras brigittae will condition themselves for spawning spontaneously — eggs and fry may appear among the plants without any dedicated breeding setup required.

Related Reading

• How to Breed Exclamation Point Rasboras: Tiny Eggs, Big Patience
• Exclamation Point Rasbora Care Guide: Boraras Urophthalmoides
• Exclamation Point Rasbora Care Guide: Brigittae Nano Gem
• Exclamation Point Rasbora Care Guide: Tiny and Eye-Catching
• Focal Point Placement in Aquascaping: Where the Eye Should Land