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2.6 ARTIFICIAL SEA SALTS:
Of all the elements present in the water used to run the tank, aquarium salt, in the form bought from pet stores, is the major constituent we rely on to adjust the quality of raw or treated water, to make it suitable for fish, corals and invertebrates.
Seawater is a very complex fluid. It contains not only inorganic elements, but also a great number of organic ones, as well as very small lifeforms (microscopic). In nature around the reefs, the chemistry of seawater changes very little. All parameters are nearly constant. This is universally so, not just around one reef. The animals are, as a result, not used to deal with changes, or water chemistry that varies from day to day, or hour to hour.
This is also the reason why many authors, including myself, recommend that conditions in the aquarium, especially the reef aquarium, should be kept as stable as possible at all times. Even minor variations can stress the animal life too much, and can result in loss of life or outbreaks of disease, because of the reduced ability of the lifeforms to deal with parasitic attacks. Marine lifeforms are just not as resilient as their fresh water counterparts, especially if they are stressed to begin with from shipping, being in bags while you transport them home, coming from aquariums with totally different water conditions, and so on. The reasons are too numerous to mention all.
Seawater contains both major and minor elements. The major elements make up 99 percent of the mix. These inorganic elements are: sodium chloride, magnesium chloride, magnesium sulfate, calcium sulfate, potassium sulfate, calcium carbonate, and bromide salts. These elements are always present, and in the same proportion, regardless of where the seawater came from. Where individual differences occur, is in the concentration of the minor elements, also called trace elements, and the organic compounds and microscopic lifeforms. These vary from reef to reef.
It is usually said that seawater contains all known chemical elements, albeit some only in very minute quantities. This obviously makes it very difficult to recreate seawater. Artificial seawater is, therefore, only a distant cousin of the real thing, yet close enough for us to be able to maintain animals in it for extended periods of time, providing we keep it at a level of purity commensurate with the requirements of the animal life present in the tank.
While we know that certain elements are necessary for the survival of fish, corals, invertebrates and algae, a great number of elements may, or may not, be crucial to the survival of the lifeforms kept.
This complicates the manufacturing process of artificial sea salts a great deal. Indeed, which elements should be included, and which ones should be left out? Typically artificial sea salts will contain around 70 different trace elements, and time has proven that such is enough to maintain reef tanks.
Because many of these elements will not dissolve instantaneously, it is recommended that artificial seawater be prepared several hours before it is actually being used. Twenty-four hours is not uncommon. This allows the water to which the salt has been added to stabilize, and be reoxygenated by means of a small air pump and an air stone. It also makes it less harsh because the chemical reactions that take place when the salt and the water are mixed, have reached the end of their course. You may consider this a minor point. It is not. Attention to detail is often what makes the difference between a reef tank that runs well, and one that looks vibrant and in super condition.
Many of the elements present in the artificial seawater that you have prepared function as nutrients for the lifeforms that you keep. As such, they are depleted as time goes on. This is also the reason why many authors recommend that trace elements should be added from time to time, to make up for the deficit. Some nutrients, or should we say trace elements, are known to be of great importance to algae, bacteria and invertebrates. They include, amongst others: iodine, strontium, molybdenum, iron, zinc, cobalt, and others. Because they are all depleted rather rapidly, the discerning hobbyist should replace them on a regular basis. Commercial products are available that allow you to do so. My own company, Thiel Aqua Tech, markets an iodine supplement, a strontium-molybdenum one called KSM, and our vitamins contain extra B-12, a major source of cobalt.
Whereas nutrients are depleted, pollutants increase as soon as you place animals in the aquarium. Pollutants reduce the water quality, stress the tank lifeforms, and need to be removed at all cost. This is the reason for the various types of filtration that we will be advocating and discussing in this book. Keeping the water in the aquarium as close as we can to seawater, is what filtration is all about.
Since aquarium salt will, for a large part, determine the quality of the end mixture in which you place the lifeforms, it is important that you select it carefully. Many brands are available. Some are regional, others are sold nationwide. Most are of excellent quality.
When it comes to reef tanks, however, we should place some extra requisites on the salt we use. The reasons are multiple, but the main one is that the corals and invertebrates kept in reef tanks are not as resilient as the fish kept in fish-only tanks. Corals and invertebrates react more markedly to certain compounds that may not affect fish, or affect them to a lesser degree. Two of these compounds are nitrates and phosphates.
Good reef aquarium salt should be extremely low in both nitrates and phosphates. In fact, ideally, it should not contain any of either. How do you determine whether the salt you are using, or plan to use, fits the requirements? Such is fairly easy. All you will need is a low range nitrate test, and a low range phosphate test. Prepare a small batch of salt water, wait for a few hours while aerating the mixture, then test the sample you have prepared for NO3 and PO4. If it contains any of either, look for another salt, and test it to ensure that it is alright to use on a reef tank.
NO3 and PO4 can cause several problems in a reef tank, not the least of which is severe and uncontrollable outbreaks of micro-algae. Besides the latter, excessive amounts of NO3 will affect the appearance of your invertebrates and corals, and may shorten their life span, influence their feeding, and affect how they react and interact with their environment (the water in the tank). Recommended levels are as low as 1 ppm of N-NO3, or a maximum of 4.5 to 5 ppm of NO3. Phosphate, on the other hand, should be present in even lower amounts. I recommend levels of no more than between 0.05 ppm (1/20 ppm) to 0.1 ppm (1/10 ppm) of PO4.
The amount of salt you add to the water determines the salinity, or specific gravity. Around natural reefs the salinity is 35 ppt (parts per thousand), or a specific gravity of 1.023 at 76 degrees Fahrenheit. You should try to maintain a similar salinity in your reef tank. Many hobbyists lower the salinity in an effort to stave off parasites and parasitic infestations. The reasoning is that at lower salinities parasites do not thrive as well as at higher ones, while fish are not as stressed, because they have to work less at maintaining their internal salt balance. This sounds good in theory. In actual fact my experience is that it does not make any difference whatsoever, and that most corals, and invertebrates, do better at the higher salinity of 35 ppt. I maintain all my tanks at that salinity. Those who have seem my tanks can attest to the fact that they all do extremely well, and that all corals, anemones, and other lifeforms all open to very large sizes. Besides, your protein skimmer will perform at its most efficient level if the salinity is at 35 ppt.
Stay away from generic salts, shoddily packed material, or varieties sold in bulk quantities and without a name. You have no way of knowing whether, in fact, they are even meant for salt water aquariums. Pure NaCl, sodium chloride, or salt, is of no value for a reef tank. Far too many chemical components are missing. Buffers especially, in the form of carbonates and bicarbonates, are an absolute must. They are the compounds that will result in a pH that is acceptable for a reef tank, and a carbonate hardness that is at least in the right range. Without such buffers the KH (carbonate hardness) and the pH may be totally off kilter. This will seriously damage the lifeforms you keep in the aquarium, especially the corals and the invertebrates.
Check your salinity on a regular basis. Evaporation will result in an increase (since salt does not evaporate, only water). On the other hand, loss of salt occurs in skimmers (see later) and also due to salt creep in various areas of the tank or filters. I check mine just about every day, but I use a salinometer, a modified refractometer that indicates salinity in parts per thousand as well. This is a highly accurate device, and gives instantaneous results. All I have to do is place about 5 drops of aquarium water on the front of the instrument, close the lid, and look through the visor to determine what the salinity actually is. Because these instruments are so easy to use, you are more likely to check your salinity frequently, and make adjustments whenever required. This increases the stability of the aquarium water chemistry. And in reef tanks, stability is the key to long term success (Thiel, 1985).
Most hobbyists use hydrometers to measure the specific gravity, rather than measuring the actual salinity. Both are, of course, acceptable ways of going about measuring whether the levels are correct. Keep in mind that you must adjust for temperature if you use a hydrometer. Indeed s.g. (specific gravity) is temperature dependent. Martin Moe Jr. and Stephen Spotte have both published charts that allow you to easily make the necessary adjustments in their books The Marine Aquarium Handbook (Green Turtle Press), respectively Seawater Aquariums, A Captive Environment (Wiley InterScience).
As an ancillary to the fact that trace elements are continuously depleted by invertebrates, fish, corals, and algae, it is of utmost importance to siphon out any dead algae that you notice in the tank immediately. Indeed, scientific studies have demonstrated that algae can store trace elements. They can do so in concentrations far greater than what these normally are in the water. When algae die off, they release these large amounts of elements back in to the tank. The larger concentrations can be noxious and can result in stress and damage to the animals you keep in the tank.
In addition to removing the dead or dying algae, I also recommend a 15 percent water change to reduce the concentration of such elements even further. If the amount of algae that died is large, at least two such water changes should be performed within a six hour time span.
Don't let this lead you to believe that keeping macro-algae is dangerous, or not desirable. On the contrary. Macro-algae are beneficial in any tank, as they assist in oxygenating the water during the day, remove certain pollutants by absorbing them, reduce nitrate and phosphate levels, and may leach antibiotic like substances in the water that reduce parasite and similar problems. A large section on macro-algae is included at the end of this book. It should give those of you who want to culture various species, all the information necessary to do so with success, and with an understanding of what is required to keep them alive. Algae is a very large subject to cover in just one chapter. If you are truly interested in macro-algae you may wish to read some of the excellent books that exist on the subject. The ones I particularly recommend to anyone who asks me are:
and as reference works the two books by Prof. William Randolph Taylor, Marine Algae, published by The University of Michigan Press, used by scientists worldwide for the identification of micro and macro-algae.
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