Why Discus Are Called the King of the Aquarium
Discus fish (Symphysodon spp.) earned their royal title through decades of captivating aquarists worldwide. Their disc-shaped bodies, vivid colour patterns, and almost parental intelligence set them apart from any other freshwater species. In Cambodia and across Southeast Asia, discus have become a prestige fish — seen in luxury hotel lobbies, upscale restaurants, and the tanks of serious hobbyists who understand that beauty requires investment. No other freshwater fish commands the same respect in a room.
What makes discus genuinely different is their social intelligence. They recognise their keeper, swim to the front of the tank at feeding time, and display stress through visible colour changes. A happy discus is boldly coloured with erect fins; a stressed discus turns dark and hides. This real-time feedback loop makes them uniquely interactive pets that respond to your husbandry choices within hours. Understanding this feedback is the first skill every discus keeper must develop.
The honest truth for beginners is that discus are not hard to keep — they are unforgiving of shortcuts. Everything they need is well understood: warm soft acidic water, quality food, low stress, and consistent routine. If you can commit to those four pillars, discus will thrive. If you cut corners on any one of them, you will watch your investment fade. This guide covers every pillar so you start with clear expectations rather than expensive surprises.
- ✦Visit a reputable discus supplier in Phnom Penh before buying — see the fish eating and swimming, never buy shy or dark-coloured fish
- ✦Budget at minimum $150-$300 USD for your first proper discus setup before buying a single fish
- ✦Join a Cambodia aquarium Facebook group — local keepers share supplier contacts and water tips specific to Phnom Penh tap water
Minimum Tank Size — Why 100 Litres Is the Starting Point
The absolute minimum for a pair of discus is 100 litres (roughly 90×40×50 cm), and that figure assumes excellent filtration and disciplined water changes. A single discus in a small tank is both cruel and counterproductive — these are schooling fish that develop anxiety disorders when isolated, showing symptoms like clamped fins, refusal to eat, and darkened colouration. The space requirement is not about swimming room alone; it is about water volume buffering parameter swings.
In practice, most experienced discus keepers recommend 200 litres or more as a comfortable starting tank for 4-6 fish. Larger water volume means slower parameter drift, more time between water changes, and a more stable thermal mass that holds temperature steady. In Cambodia's tropical climate, keeping a 200-litre tank at 29°C is far easier than fighting to stabilise a 60-litre tank, where a one-hour power cut can drop temperature by 2-3°C — enough to trigger a disease outbreak.
Discus are schooling fish and must be kept in groups of at least 6 for natural behaviour. A group of 6 discus needs a minimum of 300 litres to thrive long term. Yes, this is a significant investment in tank hardware before you buy a single fish. Budget for the tank, stand, canister filter, heater, and lighting before pricing the fish themselves. In Cambodia, 300-litre tank setups can be sourced from local aquarium shops in Phnom Penh for $80-$150 USD depending on glass thickness and brand.
- ✦Never buy fewer than 4 discus at once — solo or paired fish develop chronic stress that shortens their lifespan significantly
- ✦Choose a tall tank (50-60 cm height) — discus are tall-bodied fish and need vertical swimming space, standard 40 cm tanks restrict them
- ✦In Cambodia's hot climate, a 200L+ tank holds temperature more stable during power cuts — critical in areas with frequent outages
Water Temperature — 28 to 30°C Is Non-Negotiable
Discus originate from the warm, slow-moving blackwater tributaries of the Amazon basin, where water temperature ranges from 28-31°C year round. This thermal preference is not a guideline — it is a biological requirement. At temperatures below 26°C, discus become lethargic, their immune systems weaken, and they become susceptible to Hexamita (hole-in-the-head disease) and other opportunistic pathogens. Many beginner failures trace directly to keeping discus at the "tropical fish standard" of 24-26°C that works for tetras but stresses discus.
In Cambodia and Southeast Asia, ambient room temperatures of 28-35°C during the hot season actually work in your favour — you may need no heater at all from March to May. However, during the rainy season (June-October) and cool season (November-February), nighttime temperatures in Phnom Penh can drop to 20-22°C, which is dangerously cold for discus. A quality 300W heater with an accurate digital controller is essential year-round. Cheap bimetal heaters with +/-3°C variance are not acceptable for discus.
Temperature consistency matters as much as the target value. A tank that swings from 27°C at night to 31°C during the day will cause more problems than a stable 28.5°C. Invest in a quality digital thermometer with a min/max memory function so you can track swings even while you sleep. In Cambodia, where power fluctuations are common, a heater plugged into a voltage stabiliser adds an extra layer of protection for your fish and your equipment.
- ✦Use an Inkbird ITC-306 or similar digital heater controller — it eliminates the +/-2°C variance of built-in heater thermostats
- ✦Place your heater near the filter intake so warm water circulates immediately rather than stratifying near the heater only
- ✦Keep a backup heater unplugged but ready — heater failure overnight in Cambodia's cool season can wipe an entire discus colony by morning
Soft Acidic Water — the Chemistry Discus Need
Wild discus live in some of the softest, most acidic water on Earth — pH 4.5-6.5, GH under 3, TDS below 50 ppm. While captive-bred discus have adapted to somewhat harder water, they still perform best in soft acidic conditions. The target range for captive discus is pH 5.5-7.0, GH 2-8, KH 1-3, and TDS 100-250 ppm. Phnom Penh tap water is generally pH 7.0-7.5 with moderate hardness — usable if conditioned, but ideally cut with RO or rainwater to soften it.
Many Cambodia discus keepers use a 50/50 blend of tap water and RO water, which typically lands in a safe range. If you live near the Mekong or in areas with very hard tap water, a higher RO ratio of 70-80% may be necessary. Rainwater collected from a clean roof during the rainy season is also an excellent and free softening agent — just ensure you collect it after the first rain washes the roof, and store it in a clean sealed container to prevent mosquito breeding and contamination.
A TDS meter is the single most important test tool for discus keepers — at around $5-10 USD in Cambodia, it is far cheaper than test kits and gives you instant feedback on water quality. High TDS indicates dissolved minerals, waste products, or both. A rising TDS between water changes tells you whether your current change schedule is adequate. Pair it with a pH pen for a complete picture. These two tools tell you more about discus water quality than a full liquid test kit for most day-to-day management.
- ✦Buy a TDS meter first — available at aquarium shops in Phnom Penh's Russian Market area for around 10,000-15,000 KHR
- ✦Never use tap water directly without dechlorinator — Cambodia tap water contains chloramine that damages discus gills
- ✦Mix RO and tap water in a separate bucket and test before adding to the tank — never add untested water directly to a discus tank
Cost, Patience, and Realistic Expectations for Cambodia Buyers
Discus are among the most expensive freshwater fish available in Cambodia. Local farm-raised discus from Phnom Penh suppliers typically cost $5-$15 USD per fish for standard strains, while premium imported strains (Checkerboard, Snake Skin, Pigeon Blood) can reach $30-$80 USD per fish from Thai or Malaysian importers. A properly set-up 300-litre tank with 6 mid-grade discus represents a total investment of $250-$500 USD including equipment — more than many Cambodian monthly salaries. Understand this before committing.
Patience is the second currency of discus keeping. New fish should be quarantined for 3-4 weeks before joining an established colony. New tanks need 4-6 weeks to complete the nitrogen cycle before introducing discus. Newly purchased discus often refuse food for 1-2 weeks while adjusting to their new environment. Each of these waiting periods tests the resolve of beginners. The keepers who succeed are those who understand that rushing any step multiplies risk and cost.
The good news for Cambodia-based hobbyists is that the local discus community is active and supportive. Facebook groups like "Aquarium Cambodia" and "Fish Cambodia" connect buyers with trustworthy local breeders who sell healthy, acclimatised fish at fair prices. Buying from a local breeder who can share water parameters and feeding history is always preferable to buying imported fish whose transport stress history is unknown. Start with local farm-raised discus — they are already adapted to Cambodian water conditions.
- ✦Ask any seller for the exact water parameters the fish are kept in — match your tank to those conditions before buying
- ✦Budget 3 months of operating costs (food, water conditioner, electricity) before buying your first discus
- ✦Local breeders in Phnom Penh's Toul Kork and Sen Sok areas often sell quality discus directly — ask in Cambodia aquarium Facebook groups for current recommendations