Saltwater Introduction
Saltwater contains a great many salts which give it certain specific characteristics, and these must be understood by any aquarist who wishes to keep marine fish. In that care, a very high quality water is required in saltwater aquariums, especially if they contain invertebrates, particularly anemones and corals.
Temperature
The temperature of tropical saltwater varies little over the course of a day, or even a year. Furthermore, marine fish are generally more sensitive to abrupt changes. The temperature in a saltwater aquarium must, therefore, be fairly stable, remaining at around 25-26°C.
Salinity
The most important salt found in saltwater is sodium chloride (NaCl), widely used for domestic and culinary purposes, but there are plenty more. The salinity of water, i.e. the quantity of salts in the water, is expressed in ‰ or in g/liter. The mean salinity of the Earth's oceans is around 35 ‰, or approximately 35 g salts/liter.
Whatever its salinity, saltwater boasts one remarkable property: the proportion of each element is constant. Desalinated water does not therefore contain less of one or more salts, but the combination of salts is present in a lower concentration. The salinity of saltwater varies according to longitude. It is at its highest in open seas in the tropics, it is lower near coasts and after heavy rain, and it is at its lowest near the poles (due to the influence of melting snow).
Density
In saltwater aquariums, it is not the salinity of water which is measured, but the density (often expressed as specific gravity, S.G.), which can be calculated according to the following formula:
There are no units of measurements. The saltier the water, the higher its density. The density also varies according to temperature (it goes down as the temperature goes up). The table overleaf shows the relationship between salinity and density with respect to temperature, which is relatively constant (25-26°C) in aquariums. The density, expressed as specific gravity, a value which is easy to use, is all that is required to calculate salinity: it must range between 1.022 and 1.024.
Measuring Density
Density is measured with a hydrometer, whose buoyancy increases as the water gets saltier. In the aquarium trade, most hydrometers also include a thermometer. The specific gravity at water level must be read with care; in fact, it is preferable to use the hydrometer outside the aquarium, as the movement of the water makes it difficult to read. In this case, decant the water into a test tube or a transparent container (a PVC bottle, for example) and float the hydrometer in it. When it stops moving, read the value corresponding to the level of the water (1.023 in the diagram below, and not 1.022). To check whether your hydrometer is working properly, just measure the density of a distilled water: it must equal 1.000. |
The Main Components of Saltwater
Saltwater contains more than 60 elements. The main one is chloride, which amounts for more than 54% of the total mass of salts, followed by sodium, with around 30%. When these two elements bond, sodium chloride is formed. This is the main salt in saltwater, comprising around 85% of the total; the other salts therefore represent only 15 % in all, but they all play equally important role. Magnesium, sulfur, calcium, potassium, and bromide are the most abundant elements, after sodium.
The CH
Carbonate Hardness (CH) is used in saltwater, where it serves to measure the quantity of calcium and magnesium carbonates and bicarbonates present. This is crucial for maintaining the pH, and for growing corals, which have skeletons made of calcium carbonate.
pH Values
As saltwater is salty, its pH is therefore higher than that of fresh water. Pure saltwater in the middle of the ocean has a pH of 8.3- Near the coasts, this drops to about 8 or a little less, as its dilution with freshwater lowers the salt content. The pH of saltwater in an aquarium must vary between 8 and 8.5; beyond these values, animals will experience certain physiological problems.
Variations in pH in A Saltwater Aquarium
Saltwater contains a great deal of calcium carbonate and bicarbonate, and there are only slight variations in pH in a natural setting. It is a different matter in an aquarium, a restricted habitat operating as a closed cycle. The pH must not fall below 8, but a slow and regular decrease in this parameter may be seen. Why? The water in an aquarium sometimes contains too much carbon dioxide, which has a tendency to lower the pH.
What can you do? The first step is to mea-sure the CH:
- if it is under 7.2°CH, add calcium or replace some of the water. This situation is, however, fairly rare in an aquarium without corals, solely occupied by fish.
- if it is over 7.2°CH, there is an excess of carbon dioxide. Stirring of the water must therefore be increased by using diffusers or an electric pump.
The Nitrogen Cycle
This occurs in the same way in saltwater and freshwater. In a saltwater aquarium the vegetation is often less abundant than in freshwater, and so the nitrates, the end products of the nitrogen cycle, will have a tendency to accumulate. At high doses these pose little danger to fish but are toxic for invertebrates, especially corals. It is therefore important to eliminate them by partial, but regular, water changes.
Once a marine tank has been put into operation, the nitrogen cycle is slower to take effect than in a freshwater tank: around 3-4 weeks (although this is a generalization, as every aquarium is unique). Fish or other animals must not therefore be put into the water during this period, although the length of time can be reduced by various means, based on the principle of introducing bacteria. In any event, measuring the nitrite levels is an excellent indicator of the progress of the nitrogen cycle.
Once the water has been put into the tank, this parameter must be measured regularly; when the quantity of nitrites goes down close to zero, the nitrates appear and you only need to wait a few days before inserting the fish. Nevertheless, measuring the nitrites at regular intervals is still highly recommended, as long as the aquarium is in use.
Development of The Nitrogen Cycle once Saltwater Aquarium is in Operation
As soon as the water is put in the tank, the ammonia content rises until, as shown in the graph, it reaches its maximum level after 8 to 10 days. Simultaneously, the bacteria wich transform this ammonia are developing and nitrites are formed, reaching their peak around the 15th day. Other forms of bacteria also develop, converting, in turn, these nitrites into nitrates. While the nitrites disappear between the 20th and 25th days, the nitrates must be eliminated by partial water change. The establishement of this cycle requires at least 3-4 weeks. During this period the ammonia and nitrites reach levels that are sometimes ten times that of toxic doses. |
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Other Dissolved Substances
Saltwater contains more than 60 elements, some of them in microscopic amounts: for 3 example, there is 1 g/m of gold in sea water. All the solids dissolved in saltwater serve a purpose, and that is why the salts that are used to reconstitute water must be of excellent quality. Some substances can accumulate in saltwater and in high concentrations give rise to concern. This is especially true in the case of organic matter, but it is possible to eliminate them by partially changing the water or using certain devices, such as an aerator.
Calcium in Saltwater
Saltwater contains between 400 and 500 mg/liter of calcium, which is up to 20 times more than freshwater. Calcium participates in the composition of calcium carbonate (CaCO3), necessary for the formation of coral skeletons, the carapace of crustaceans, and the shells of mollusks. If you are raising these animals, the CH must be between 6,7 and 14°GH; if it is below this level, part of the water must be changes or calcium must be added. This is not necessary if there are already fish on the tank.
Turbidity
Clarity is more important in sea water than in freshwater. Tropical environments in particular contain very few dissolved solids and they are the most transparent waters on the planet. A saltwater aquarium must therefore be filtered more efficiently and to a greater extent than a freshwater tank.
The Origin of Saltwater in Saltwater Aquariums |
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Where and When To Collect Natural Saltwater?
The ideal solution would be to go to the open sea, where the water is likely to be less polluted and to have more constant characteristics. Near the coasts, the following must be avoided: urbanized or industrialized areas and ports, which are susceptible to pollution; anywhere near river mouths, estuaries, or bays, where the water is desalted; and areas of stagnant saltwater (pools at low tide) and salt marshes. Coasts with sand dunes are suitable in principle, but the water is often laden with suspended sediment. Rocky coasts are preferable regions from where water can be collected.
The best periods for collection are autumn and winter, because plankton develop in spring and tourism increases the risk of pollution in summer. Calm weather is preferable, in order to avoid suspended material, although a heavy swell reoxy-genates the water. In this case, the water can be collected 1-3 days later, the time in which the suspended material turns into sediment. However, the water must be filtered in all cases, first roughly and then more finely.
The Reconstitution of Artificial Saltwater
The quality of the fresh water used is important: it must be as pure as possible. It is best to use water with a hardness of less than 8.4, although reconstitution is still possible with higher levels, providing the CH is equal to at least 75-80% of the general hardness value. Take care to avoid water containing nitrates (often found in farming areas), to which invertebrates are very sensitive, or metals, toxic for some animals where present above certain limits.
Making Saltwater in an Aquarium, Before Putting it into Operation
Fill the aquarium with fresh water and aerate it for 24 hours. Calculate and weigh the quantity of salts to be dissolved, and then introduce them into the aquarium. Then just aerate for another 24-48 hours and check the density, adjusting it as required.
Artificial Salts |
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There have been no adverse reports to date about the use of these salts in aquariums: in those areas where accidents do occur, they are usually due to miscalculations on the part of the aquarist. Artificial sea water can be reconstituted with the help of special salts available in aquarium stores.
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Making Saltwater For Storage and Back-up
The method is the same, except that plastic food containers are generally used. The quantity of salt can be multiplied by three or four to manufacture concentrated water that will therefore occupy less storage space.
Water collected in a natural setting is transported in plastic containers, such as jerry cans. As these generally have a limited volume (under 30 liters), quite a few a required to fill an aquarium of several hundred liters. The water can be stored in these containers, protected from heat and sunlight (cellar, garage, storeroom, and attic). Some aquarist with several tanks store their water in cisterns covered with polyethylene; these are available commercially.
Adjusting The Density
• The Density is Too High
Part of the water is siphoned off - this can be stored for later use - and the softest water available is added, taking care to measure the density. When the water level of a marine aquarium goes down because of evaporation, it is not the sea water which is evaporating but the fresh water, and it is therefore the latter which must be added to make up the level.
The addition of sea water would entail
an increase in density.
• The Density is Too Low
In this case, salts must be added. These must be dissolved beforehand in a container which is then gradually emptied into the aquarium, with constant checks on the density. Both these operations must be performed with care if the aquarium already contains fish, in order to avoid causing any excessively abrupt changes that could be detrimental to the fish.
Cover all we need to know about saltwater, so we can keep marine fish.
Lot of things we should prepare to start saltwater aquarium!
Steps to be taken before the aquarium ready to receive
fish and operate.
Detail about saltwater fish species. For beginner also expert.
They difficult to keep, although there are some suitable for hobbyist.
There’s only a few of them, but the results can often be highly attractive.
Get to know, how to maintain your aquarium daily to have
a good balanced.
Essential regular activity to provides a stable, healthy environment for fish!
Follow this rules for a Successful Saltwater Aquarium.
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