Aquarium glossary

Alkalinity

Alkalinity is synonymous with KH in the aquarium context. Indicates the buffer capacity of the water against pH variations.

Alkalinity in marine aquariums (dKH)

The buffer capacity of sea water. Corals consume carbonates to build their skeleton. Critical parameter in the reef.

Aluminium in the aquarium

Metal contaminant that should not be present in aquarium water. Even in trace amounts it can damage corals and invertebrates.

Ammonia (NH3/NH4+)

Ammonia is the first product of organic decomposition in the aquarium. In non-ionised form (NH3) it is toxic even at very low concentrations.

Barium

Trace element present in sea water. It is consumed by corals and sponges. Its role is still little understood but must be monitored with ICP.

Boron

Trace element present in sea water. Important for the metabolism of corals and calcareous algae. It is monitored via ICP analysis.

Calcium (Ca)

Calcium is the fundamental building block for the growth of corals and invertebrates. In the reefs it is consumed continuously and must be constantly replenished.

Calcium-magnesium ratio

In marine aquariums the ratio between calcium and magnesium must be balanced. Magnesium allows calcium to remain in solution without precipitating.

Chlorine and chloramines

Disinfectants present in tap water. Deadly for fish, invertebrates and filter bacteria. They must always be neutralized before use.

CO2 (carbon dioxide)

CO2 is the number one nutrient for aquatic plants. Without an adequate CO2 source, plants grow poorly and algae take over.

Cobalt

Essential trace element in minimal traces. Component of vitamin B12. Important for bacteria and algae, monitored with ICP.

Copper (Cu)

Copper is extremely toxic to invertebrates and corals even at very low concentrations. It serves only as a drug treatment for some fish diseases.

Dissolved oxygen

The amount of oxygen present in the water. Essential for the respiration of fish, corals and filter bacteria.

Electrical conductivity

Measures the ability of water to conduct electrical current. It indirectly indicates the total quantity of dissolved salts and minerals.

Fluoride in the aquarium

Naturally present in sea water. In the aquarium it mainly comes from synthetic salt and tap water. Toxic in excess.

GH (general hardness)

GH measures the concentration of calcium and magnesium in water. In freshwater aquariums it is a key parameter for species compatibility.

Iodine (I)

Iodine is essential for the moulting of crustaceans and for the health of some soft corals. It is consumed quickly and must be replenished in aquariums with many invertebrates.

Iron (Fe)

Iron is an essential micronutrient for aquatic plants. The deficiency causes pale leaves with green veins. In marine aquariums it is less critical.

KH (carbonate hardness)

KH measures the ability of water to resist changes in pH. In practice it indicates how stable the system is from a chemical point of view.

Lead in aquarium

Highly toxic heavy metal. It should never be present. Deadly for invertebrates and fish even at very low concentrations.

Lithium in the aquarium

Trace element present in natural sea water. Its biological role in the aquarium is little known. It is monitored with ICP.

Magnesium (Mg)

Magnesium stabilises the balance between calcium and KH preventing spontaneous precipitation. Without adequate magnesium the Balling method does not work.

Manganese

Essential microelement for aquatic plants and for some enzymatic processes in corals. Required in minimal traces.

Molybdenum

Trace element essential for nitrogen metabolism in plants and bacteria. Required in microscopic quantities.

Nickel in the aquarium

Contaminating heavy metal. Even in small quantities it can damage corals. Its presence almost always indicates a problem to be solved.

Nitrates (NO3)

Nitrates are the end product of the nitrogen cycle. Less toxic than ammonia and nitrites but harmful if they accumulate over time.

Nitrites (NO2)

Nitrites are the intermediate product of the nitrogen cycle. Like ammonia they must be at zero in a mature aquarium.

Nitrogen for plants (nitrate as a nutrient)

In planted freshwater aquariums, nitrates are not just a waste product but the main nitrogenous nutrient for plants. Too low a level limits growth.

ORP (redox potential)

ORP measures the oxidizing power of water in millivolts. A high ORP indicates clean, well-oxygenated water. A low ORP indicates accumulation of organic substances.

PAR (Photosynthetically Active Radiation)

PAR measures the amount of light that can be used for photosynthesis. It is the most important parameter for positioning corals and aquatic plants.

pH

The pH indicates how acidic or alkaline the water is on a scale from 0 to 14. For aquariums the ideal value depends on the type of aquarium and the species hosted.

Phosphates (PO4)

Phosphates are nutrients that in excess fuel algae growth. On the reef they must be kept very low. In planted freshwater aquariums they are needed for the plants.

Potassium (K)

Potassium is an often overlooked trace element in marine aquariums. It contributes to the colour of corals, especially intense reds and purples.

Salinity

Salinity indicates the total concentration of salts dissolved in water. It is measured in PSU, ppt or by specific gravity (SG).

Silicates (SiO2)

Silicates fuel the growth of diatoms (brown algae). They are common in new aquariums and can enter from unfiltered mains water.

Sodium

The most abundant element in sea water after chlorine. It contributes to the salinity and osmotic balance of aquatic organisms.

Specific gravity (SG)

Specific gravity is an alternative way to measure salinity. Indicates the ratio between the density of salt water and that of pure water.

Strontium (Sr)

Strontium is a trace element that contributes to the calcification of corals. It is consumed slowly and must be replenished in intensive reef aquariums.

Sulfates

Ions naturally present in sea and fresh water. In marine aquariums they are the third most concentrated component after chloride and sodium.

TDS (total dissolved solids)

TDS measures the total quantity of substances dissolved in water. It is mainly used to check that the reverse osmosis system is working correctly.

Temperature

Temperature influences every biological process in the aquarium: metabolism, dissolved oxygen, bacterial activity, growth of corals and plants.

Tin (Sn) in aquariums

Contaminating heavy metal. It should not be present in the aquarium water. Toxic for corals and invertebrates.

Vanadium in aquarium

Trace element present in sea water in traces. Limited but monitored biological role in ICP analyzes as a quality indicator.

Zinc in the aquarium

Essential trace element in minimal traces for enzymes and biological processes. In excess it becomes toxic, especially for invertebrates and corals.