New 🐟 Mercury Safety Guide & Omega-3 Rankings Updated for 2026. View Omega-3 Rankings →

🌿 Sustainable Seafood ⚡ Omega-3 Rankings 🔬 Mercury Safety 🏆 World Records 🎣 Fishing Licenses

API Docs

Get API Key →

Aquarist Reference

Water Chemistry Deep Dive

Every water parameter explained in depth. pH, KH, GH, ammonia, nitrite, nitrate, TDS, dissolved oxygen, salinity - what each one is, why it matters, how to test, and how to adjust it up or down.

💧 37 parameters 🧪 5 categories

Chemistry 10 topics

Ammonium (NH4+) in Planted Tanks

The plant-preferred nitrogen form - many aquatic plants absorb ammonium faster than nitrate, and som...

Chlorine & Chloramine

Municipal water disinfectants that are highly toxic to fish - must be neutralised via water conditio...

The electrical conductivity of water - directly proportional to dissolved ion concentration; a more...

µS/cm CONDUCTIVITY

Copper (Toxicity)

A heavy metal toxic to fish and lethal to invertebrates - but a primary treatment for many marine pa...

Ionic Composition of Seawater

The eight major ions that account for 99% of seawater composition - sodium, chloride, magnesium, sul...

ppm profile SEAWATER_IONS

ORP (Oxidation-Reduction Potential)

A measure of the waters oxidising vs reducing chemistry - reef tanks target 300-400 mV; lower indica...

A measure of water acidity/alkalinity on a 0-14 scale - pH 7 is neutral, below is acidic, above is b...

The total dissolved salt content of saltwater - typically measured as specific gravity (SG) or parts...

ppt or SG SALINITY

Tannins (Humic Substances)

Organic compounds released by botanicals (leaves, wood) that stain water amber and provide antimicro...

visible discoloration TANNINS

TDS (Total Dissolved Solids)

The total concentration of dissolved minerals, salts, and organics in water - a quick indicator of w...

Cycle 7 topics

Ammonia (NH3/NH4+)

The primary nitrogenous waste of fish - highly toxic and the number one killer in newly-set-up aquar...

Denitrification

The anaerobic bacterial process that converts nitrate into harmless nitrogen gas - the final stage o...

process DENITRIFICATION

New Tank Syndrome

The predictable ammonia and nitrite spikes that kill fish added to un-cycled tanks - one of the most...

NH3 vs NH4+ (Ammonia Chemistry)

The critical distinction between toxic un-ionised ammonia (NH3) and less toxic ionised ammonium (NH4...

The end product of the nitrogen cycle - much less toxic than ammonia or nitrite but still stressful...

The second stage of the nitrogen cycle - less immediately toxic than ammonia but still deadly, causi...

Nitrogen Cycle Overview

The complete biological process by which fish waste ammonia is converted to nitrite to nitrate - the...

cyclical N_CYCLE

Gas 4 topics

Carbon dioxide dissolved in aquarium water - essential nutrient in planted tanks (20-30 ppm target)...

Dissolved Oxygen

The amount of oxygen gas dissolved in water - the fundamental requirement of aquatic life.

Nitrogen Supersaturation

When water contains more dissolved nitrogen gas than atmospheric equilibrium - can cause gas bubble...

percentage N2_SAT

Oxygen Debt & Recovery

The oxygen deficit built up during burst activity that must be repaid during recovery - a physiologi...

Mineral 12 topics

Boron / Borate Buffering

Borate ions in seawater contribute meaningfully to alkalinity buffering and are consumed by some bio...

Dissolved calcium ions in reef systems - the primary building material corals use to build their ske...

GH (General Hardness)

A measure of dissolved calcium and magnesium in water - essential minerals for fish osmoregulation,...

Iodine (Reef Trace)

A trace element used by reef invertebrates - particularly important for shrimp molting, macroalgae,...

A trace element essential for plant chlorophyll production - deficiency causes yellowing leaves and...

KH (Carbonate Hardness)

The buffering capacity of water against pH swings - measured as bicarbonate and carbonate ions. High...

KH vs Alkalinity Distinction

The precise distinction between carbonate hardness (KH) and total alkalinity - important for reef pr...

dKH vs meq/L KH_ALK

A critical reef parameter - magnesium interacts with calcium and alkalinity to enable coral skeleton...

A limiting nutrient in reef tanks (target 0.02-0.1 ppm) but a required fertiliser in planted tanks (...

Potassium in Aquaria

The plant macronutrient often deficient in aquariums - a key ingredient in planted-tank fertilisatio...

Dissolved silica - a diatom nutrient that fuels brown algae blooms. Common in tap water and new reef...

Strontium (Reef Trace)

A reef trace element consumed by corals and coralline algae for calcification - part of the classic...

Physical 4 topics

Water temperature - controls metabolic rate, oxygen solubility, and disease resistance.

F or C TEMPERATURE

Physiological damage caused by rapid temperature change - a sudden 5 C shift can be fatal to fish ad...

delta_c THERMAL_SHOCK

Thermal Stratification

The seasonal layering of warm surface water and cold deep water in lakes - creates distinct habitat...

layered STRATIFICATION

Water Column Mixing

The turbulent mixing of water within a tank or lake - ensures uniform temperature, oxygen, and disso...