Salinity: the Basics
If you’re starting your adventure with marine aquaristics, it’s worth learning what salinity is. Salinity is the general mineralization of seawater, specifying the solids content in grams per 1 kg of seawater. Generally speaking, they’re minerals dissolved in water.
In seawater we find the most of the following ingredients: sodium chloride 77.8%, magnesium chloride 10.90%, magnesium sulphate 4.70%, calcium sulphate 3.60%, potassium sulphate 2.50%, calcium carbonate 0.35%, magnesium bromide 0.22%. Together, they account for over 99.5%, the rest are microelements.
The table below shows the content of these elements in seawater:
Element | ppm | Element | ppm | Element | ppm |
Sodium Na | 10800 | Zinc Zn | 0.005 | Praseodymium Pr | 0.00000064 |
Chlorine Cl | 19400 | Gallium Ga | 0.00003 | Neodymium Nd | 0.0000028 |
Magnesium Mg | 1290 | Germanium Ge | 0.00006 | Samarium Sm | 0.00000045 |
Sulfur S | 904 | Arsenic As | 0.0026 | Europium Eu | 0.0000013 |
392 | Selenium Se | 0.0009 | Gadolinium Gd | 0.0000007 | |
Calcium Ca | 411 | Krypton Kr | 0.00021 | Terbium Tb | 0.00000014 |
Bromine Br | 67.3 | Rubidium Rb | 0.120 | Dysprosium Dy | 0.00000091 |
Helium He | 0.0000072 | Strontium Sr | 8.1 | Holmium Ho | 0.00000022 |
Lithium Li | 0.170 | Yttrium Y | 0.000013 | Erbium Er | 0.00000087 |
Beryllium Be | 0.0000006 | Zirconium Zr | 0.000026 | Thulium Tm | 0.00000017 |
Boron B | 4.450 | Niobium Nb | 0.000015 | Ytterbium Yb | 0.00000082 |
Carbon C | 28.0 | Molybdenum Mo | 0.01 | Lutetium Lu | 0.00000015 |
Nitrogen N | 15.5 | Ruthenium Ru | 0.0000007 | Hafnium Hf | <0.000008 |
Fluorine F | 13 | Rhodium Rh |
| Tantalum Ta | <0.0000025 |
Neon Ne | 0.00012 | Palladium Pd |
| Tungsten W | <0.000001 |
Aluminium Al | 0.001 | Argentum (silver) Ag | 0.00028 | Rhenium Re | 0.0000084 |
Silicon Si | 2.9 | Cadmium Cd | 0.00011 | Osmium Os |
|
Phosphorus P | 0.088 | Indium In | . | Iridium Ir |
|
Argon Ar | 0.450 | Stannum (tin) Sn | 0.00081 | Platinum Pt |
|
Scandium Sc | <0.000004 | Antimony Sb | 0.00033 | Aurum (gold) Au | 0.000011 |
Titanium Ti | 0.001 | Tellurium Te |
| Mercury Hg | 0.00015 |
Vanadium V | 0.0019 | Iodine I | 0.064 | Thallium Tl |
|
Chromium Cr | 0.0002 | Xenon Xe | 0.000047 | Lead Pb | 0.00003 |
Manganese Mn | 0.0004 | Cesium Cs | 0.0003 | Bismuth Bi | 0.00002 |
Iron (Ferrum) Fe | 0.0034 | Barium Ba | 0.021 | Thorium Th | 0.0000004 |
Cobalt Co | 0.00039 | Lanthanum La | 0.0000029 | Uranium U | 0.0033 |
Nickel Ni | 0.0066 | Cerium Ce | 0.0000012 | Plutonium Pu |
|
Copper Cu | 0.0009 |
By keeping the salinity constant in a marine aquarium, we maintain a given concentration of minerals in the seawater. Check out this article to learn how to keep salinity at a stable level: Link here
In marine aquariums we usually keep the salinity between 32-35 ppt. It’s assumed that lower salinity is better for soft corals and fish, while a value of 35 ppt is appropriate for SPS corals.
About the author
Marek Protasewicz
Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.
My social media profiles
