Chili Rasbora — Cambodia's Favorite Nano Fish
Boraras brigittae, commonly known as the Chili Rasbora, is arguably the best nano fish available in Southeast Asia. Reaching a maximum size of 1.5 cm, these vivid red micro-fish are perfectly suited to tanks as small as 10 liters when kept in groups of 8-12 individuals. Their intense scarlet coloration intensifies under tannin-stained blackwater conditions — a simple setup to replicate by adding a small piece of Indian almond leaf or a handful of dried oak leaves to the substrate.
Chili Rasboras are native to the peat swamp forests of Borneo and thrive in soft, slightly acidic water with a pH of 5.5-7.0 and a temperature of 22-28°C. Cambodia's tap water in most cities is moderately hard with a pH around 7.2-7.6, which is acceptable for Chili Rasboras with some blackwater conditioning. They are omnivores that accept micro-pellets, baby brine shrimp, and crushed flake food enthusiastically, making feeding straightforward for beginners.
The main challenge with Chili Rasboras in Cambodia is sourcing healthy stock. Many fish imported from Thailand or Malaysia arrive stressed and underfed at local markets. Select fish that are actively schooling, showing bright color, and eating at the point of sale. Avoid fish with clamped fins, white spots, or lethargic behavior. Quarantine new Chili Rasboras for 2 weeks in a separate tank before adding them to your display nano tank.
- ✦Keep at least 8 Chili Rasboras — groups below 6 become stressed and lose color
- ✦Add 1-2 Indian almond leaves to a Chili Rasbora tank — tannins enhance color and replicate their natural blackwater habitat
- ✦Chili Rasboras tolerate Cambodia's warm summers (up to 30°C) better than most other nano species
Ember Tetra — The Warm-Glow Alternative
Hyphessobrycon amandae, the Ember Tetra, is a Brazilian nano fish reaching 1.8-2 cm in length and displaying a warm amber-orange body color that photographs beautifully under planted tank lighting. Like Chili Rasboras, Ember Tetras are schooling fish that should be kept in groups of at least 8, ideally 10-15 in a 15-liter planted setup. Their slightly larger size compared to Chili Rasboras makes them slightly easier for beginners to observe and feed without needing specialty micro-foods.
Ember Tetras prefer soft, slightly acidic water but are notably more adaptable than Chili Rasboras and will thrive in neutral tap water with a pH of 6.5-7.5 and temperatures of 24-30°C. This adaptability makes them one of the most forgiving nano fish for beginners managing Cambodia's variable tap water quality. They accept most small commercial foods including micro-pellets, fine-grade flake, and frozen baby brine shrimp.
One characteristic that makes Ember Tetras particularly suited to planted nano tanks is their tendency to swim in the middle and lower thirds of the water column, threading through plant leaves in a naturalistic way. Pairing a school of Ember Tetras with a few Pygmy Corydoras on the bottom creates a complete, multi-level stocking picture in a tank as small as 20 liters. Both species share similar water parameter preferences, making maintenance straightforward.
- ✦Ember Tetras show their best color under warm-spectrum lighting (3000-4000K) rather than the standard 6500K daylight bulbs
- ✦Feed small amounts twice daily rather than one large feeding — this reduces waste and improves growth
- ✦Ember Tetras are sensitive to ammonia spikes; never add them to an uncycled tank
Pygmy Corydoras — The Essential Nano Bottom Cleaner
Corydoras pygmaeus is one of three species collectively called Pygmy Corydoras, all reaching 2-2.5 cm at maximum adult size. Unlike their larger Corydoras cousins which require tanks of 60 liters or more, Pygmy Corydoras are genuinely nano-compatible and provide the vital bottom-cleaning function that keeps substrate detritus from decomposing into ammonia. A group of 5-6 Pygmy Corydoras is recommended for any planted nano tank larger than 10 liters.
Pygmy Corydoras display an unusual behavior among Corydoras species — they are midwater swimmers as much as bottom dwellers, frequently darting up to feed at the surface before returning to the substrate. This active, playful behavior adds visual interest to a nano tank at all water levels. They are peaceful community fish that coexist well with Chili Rasboras, Ember Tetras, and shrimp colonies, though they should not be kept with any fish large enough to view them as food.
Like all Corydoras, Pygmy Corydoras breathe atmospheric air occasionally by darting to the surface. This is normal behavior and not a sign of oxygen deficiency. They require a fine sand or smooth rounded-pebble substrate — sharp gravel damages their delicate barbels over time. Pool filter sand, widely available at building supply shops in Phnom Penh, is an ideal and affordable substrate option for Pygmy Corydoras tanks.
- ✦Keep Pygmy Corydoras in groups of at least 5 — lone individuals become stressed and prone to disease
- ✦Feed sinking wafers or sinking micro-pellets to ensure bottom dwellers get adequate nutrition
- ✦Fine pool sand substrate is available at Phnom Penh hardware stores for approximately 5,000-8,000 KHR per kilogram
Endler's Livebearer — Hardy and Colorful Nano Fish
Poecilia wingei, the Endler's Livebearer, is a small livebearer from Venezuela that reaches 2-2.5 cm for males and 3-3.5 cm for females. Males display extraordinary color variety — orange, green, black, and blue patterns that rival full-sized fancy guppies in visual impact. Endlers are among the hardiest nano fish available, tolerating a wide range of water parameters including Cambodia's typical pH 7.2-7.6 tap water, temperatures from 24-32°C, and moderate hardness.
One important consideration with Endlers is their prolific breeding. A single pair will produce 5-20 live fry every 23-24 days, and without predation or removal, a nano tank can become severely overstocked within a few months. The simplest management strategy is to keep only males, which display all the color with none of the population explosion. A group of 6-8 male Endlers in a 15-liter planted tank is a beginner-friendly, low-maintenance, visually striking setup.
Endlers are also notably tolerant of the higher temperatures Cambodia experiences in the hot season — males remain active and colorful at 31-32°C where many other nano species begin showing heat stress. This makes Endlers a particularly practical choice for Cambodia hobbyists who do not want to manage cooling equipment. They accept virtually any small food, making them one of the easiest nano fish to feed correctly.
- ✦Keep only males if you do not want to manage fry — mixed-sex Endlers will overstock a nano tank within 3 months
- ✦Endlers cross-breed readily with guppies — keep them separated to maintain pure Endler strains
- ✦Endlers tolerate Cambodia's hot season (32°C) better than any other popular nano fish species
Sparkling Gourami — The Jewel of the Nano Tank
Trichopsis pumila, the Sparkling Gourami, is a labyrinth fish reaching 3-4 cm that produces audible chirping and croaking sounds during courtship — an unusual feature that delights fishkeepers of all experience levels. Males display iridescent blue-green spots on their fins that literally sparkle when light catches them at the right angle, explaining the common name. A pair or a small group of 3-4 Sparkling Gouramis makes a compelling centerpiece for a 15-20 liter heavily planted nano tank.
Sparkling Gouramis are native to Southeast Asia, including the Mekong basin that runs through Cambodia, making them one of the few nano fish with genuine regional relevance for Cambodian hobbyists. They are found in shallow, heavily vegetated rice paddies, forest pools, and slow-moving streams — conditions that a planted nano tank replicates closely. They prefer calm water with minimal surface agitation, which aligns well with the gentle sponge filtration recommended for nano tanks.
Male Sparkling Gouramis display mild territorial behavior toward each other, but in a well-planted 20-liter tank with multiple hiding spots created by dense vegetation, a group of 2-3 males and 1-2 females coexists peacefully. They are compatible with Chili Rasboras, small Corydoras, and Neocaridina shrimp. Like all labyrinth fish, they occasionally gulp air at the surface — this is normal and not an indicator of poor water quality.
- ✦Sparkling Gouramis are native to Cambodia's Mekong drainage — they are perfectly adapted to local climate conditions
- ✦Dense floating plants like frogbit or water sprite create the surface cover Sparkling Gouramis prefer
- ✦Males will chirp during spawning — the sound is faint but audible in a quiet room, which surprises new keepers pleasantly
Bioload Math and Why to Avoid Goldfish in Nano Tanks
Bioload is the total biological oxygen demand and waste production of all livestock in a tank. For nano tanks, bioload math is critical because there is so little water volume to buffer waste accumulation. A simple bioload index assigns each nano fish species a score based on its metabolic rate and waste production: Chili Rasboras score 1 point each, Ember Tetras and Endlers score 1.5 points each, Pygmy Corydoras score 2 points each, and Sparkling Gouramis score 2.5 points each. A 15-liter cycled tank with a properly sized filter can support approximately 15-18 bioload points.
Using this framework, a 15-liter tank could house 10 Chili Rasboras and 4 Pygmy Corydoras (10 + 8 = 18 points), or 8 Ember Tetras and 3 Sparkling Gouramis (12 + 7.5 = 19.5 points — slightly over, requiring a strong filter and frequent water changes). The bioload index is a guideline, not a guarantee — actual water quality depends heavily on feeding amounts, filtration efficiency, and how recently the tank was serviced.
Goldfish must never be kept in nano tanks, regardless of their current small size. Common goldfish grow to 30+ cm and produce extraordinary amounts of ammonia — a single juvenile goldfish produces more waste than 20 Chili Rasboras. Fancy goldfish are equally unsuitable for nano tanks. The premise that small goldfish are appropriate for small bowls or tanks is one of the most destructive myths in fishkeeping, causing enormous suffering to millions of fish kept in inadequate conditions. In Cambodia, goldfish sold at markets are frequently kept in bowls — this is not a model to follow.
- ✦Calculate your bioload before buying fish — write the number on a sticky note on the tank so you remember the limit
- ✦Goldfish are coldwater fish requiring 20+ liters per fish minimum — never put them in a nano tank regardless of their current size
- ✦When in doubt, stock less — a slightly understocked nano tank is infinitely more stable than an overstocked one