The Six Parameters That Control Fish Health
Six measurements define whether your aquarium water is safe or slowly poisoning your fish: ammonia, nitrite, nitrate, pH, hardness (GH/KH), and temperature. Of these, ammonia and nitrite are the most immediately dangerous. They can kill fish within hours at moderate levels and damage organs at levels that appear safe but are chronically present.
In Cambodia, fishkeepers often measure nothing and rely on the fish's behavior to signal problems. This is an extremely late warning system — by the time a fish visibly shows stress from poor water, it has already sustained organ damage. A $10 liquid test kit used regularly saves fish and eliminates guesswork.
Ammonia: The Silent Killer
Ammonia (NH3) is the first waste product of fish metabolism and decomposing food. It is produced constantly in every fish tank and is toxic even at 0.25 ppm (parts per million). At 1 ppm, it causes gill damage and immune suppression. At 2+ ppm, it kills within 24-48 hours.
In a cycled aquarium, beneficial bacteria (Nitrosomonas species) convert ammonia to nitrite within 24 hours. If these bacteria are absent (new tank), killed (chlorine, medication), or overwhelmed (overstocking, overfeeding), ammonia accumulates. Target level: 0 ppm at all times.
If ammonia reads above 0 in a running tank, perform an immediate 30% water change with dechlorinated water, remove any uneaten food and dead plant material, and check if you recently cleaned the filter with tap water (which kills bacteria). Add Seachem Prime to temporarily detoxify ammonia while the bacterial colony recovers.
- ✦Never clean filter media in tap water — rinse only in old tank water
- ✦Seachem Prime detoxifies ammonia for 24-48 hours — use during emergencies
- ✦Ammonia spikes most often after overfeeding or adding too many fish at once
Nitrite and Nitrate
Nitrite (NO2) is ammonia converted by Nitrosomonas bacteria — it is also toxic, interfering with the blood's ability to carry oxygen. Fish experiencing nitrite poisoning show rapid gill movement, gasping at the surface, and brown-tinged gills (methemoglobin). Target level: 0 ppm.
Nitrate (NO3) is the end product of biological filtration, converted from nitrite by Nitrospira bacteria. Nitrate is far less toxic than ammonia or nitrite but accumulates over time. Above 40 ppm, it stresses sensitive species and promotes algae. Target level for most tropical fish: below 20 ppm. Control through regular water changes and live plants.
The relationship between ammonia-nitrite-nitrate is called the nitrogen cycle. Understanding this cycle is the difference between a healthy thriving aquarium and one where fish constantly die for "no apparent reason." Every Cambodian fishkeeper who sets up a new tank should cycle it properly before adding any fish.
pH: Acid-Base Balance
pH measures the hydrogen ion concentration in water on a scale from 0-14, where 7 is neutral, below 7 is acidic, and above 7 is alkaline. Most tropical fish sold in Cambodia are tolerant of a pH range of 6.5-7.5. Stability is more important than exact numbers — a fish that lives at pH 7.2 is far healthier than one whose tank swings between 6.5 and 7.5 daily.
Cambodian tap water typically has a pH between 7.0 and 7.5. This is suitable for bettas, guppies, tetras, goldfish, and most common aquarium fish without any adjustment. However, high-CO2 planted tanks can push pH down toward 6.5 during daylight hours as plants absorb CO2. This is normal and harmless to CO2-adapted species.
Never aggressively adjust pH with pH-up or pH-down chemicals. These products cause dangerous pH swings as they interact with the water's carbonate buffer. If your tap water pH is outside the range for your specific fish, research appropriate solutions (peat filtration for soft-water species, crushed coral for cichlids).
Hardness (GH and KH)
General hardness (GH) measures dissolved calcium and magnesium. It affects fish mineral metabolism, plant growth, and egg fertility in breeding fish. Carbonate hardness (KH) measures bicarbonate and carbonate ions — it acts as a pH buffer, resisting changes in pH.
Cambodia's provincial water varies from very soft (wells in sandy soil, 30-50 ppm GH) to moderately hard (limestone regions, 150-200 ppm). Most common aquarium fish in Cambodia are fine in 80-200 ppm GH. Discus and wild-caught bettas prefer very soft water (20-50 ppm). African cichlids need very hard water (200-400 ppm).
If you do not know your tap water hardness, take a sample to an aquarium shop in Phnom Penh — most will test it for free or a small fee.
Temperature for Cambodia Fish Tanks
Cambodia's ambient temperature of 28-35°C suits most tropical fish year-round without a heater. However, air-conditioned rooms, especially at night, can drop tank water to 22-24°C in modern apartments. For bettas (need 26-28°C), guppies (24-28°C), and discus (28-30°C), a heater is necessary in air-conditioned environments.
Temperature consistency matters more than exact value. Fish adapt to slightly cooler or warmer water over time, but rapid changes of 3-5°C within hours (from heavy rain cooling an open-air tank, or AC turning on) trigger severe immune stress and open the door to disease outbreaks. A heater with a thermostat prevents these swings even when room temperature fluctuates.