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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.

💧 22 parameters 🧪 5 categories

Chemistry 8 topics

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...

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 3 topics

Ammonia (NH3/NH4+)

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

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...

Gas 2 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.

Mineral 8 topics

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...

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 (...

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

Physical 1 topic

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

F or C TEMPERATURE