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Aquarium Water QualityContents
The basic principles Water is an essential part of fish keeping “equipment”, and is probably the most misunderstood. Many of the problems that occur in the fresh water aquarium are usually associated with water quality. The fish that we keep in our aquariums originate from all over the world. It is therefore necessary for the aspiring fish keeper to have an understanding of how the chemistry and quality of the water varies from region to region. You will need to understand and be able to alter your own local water to suit the needs of your fish. You MUST regularly monitor your water to guard against any build up of harmful pollutants, as well as its general condition. Natural bodies of water, such as lakes and rivers, are by nature very stable environments. Their large volumes of water counteract any changes in water quality, and it is this dilution effect that makes such changes hardly noticeable. Tropical freshwater fish have evolved to live in these stable conditions, and are therefore very susceptible to any change they may encounter in water chemistry. Although we like to regard our aquariums as a small-scale reproduction of life in a lake or river, we must consider the much smaller volume of water our fish have to live in. Any changes in water chemistry will have a greater impact in the aquarium than in nature, due to a much lower dilution effect. Fish will detect even the smallest decline in water quality, and will often show signs of irritation and stress. Water As you probably know water is a compound of hydrogen and oxygen, at the ratio of 2:1, hence H2O, and, although life is dependant on water, “pure water” will not support life. Water must contain certain salts if it is to support life at all. Fortunately, water is highly adept at dissolving gases and solids, and it is this ability to readily dissolve other substances that makes it able to support life (water will also readily dissolve pollutants, which must be controlled, I’ll get to that later). It is because of this capacity to dissolve numerous substances in large amounts that pure water rarely occurs in nature. As water falls to earth as rain or snow it will absorb from the atmosphere varying amounts of carbon dioxide and other gases, as well as traces of organic and inorganic matter. (If you are using rainwater for your aquarium, be sure to filter it through carbon for 24 hours first). Upon reaching the earth’s surface, the water will follow two paths. Some of the water will infiltrate the soil, a part of which becomes soil moisture, which will evaporate directly, or be used by the roots of vegetation. Water that overcomes these forces in the soil profile will percolate deeper and become a part of the groundwater reservoir, the surface of which is known as the water table. The other path which rainwater will take is over the surface, which is termed as surface run off, and will run directly into streams, rivers, and landlocked bodies of water, such as lakes. Most natural waters contain dissolved salts, which are consequently found in tap water. Natural water will also contain suspended and dissolved impurities, which is why it must be treated before it is fit for us to drink. The amounts of salts dissolved in the water determine whether it is hard or soft. Water that is in constant contact with substances such as limestone or chalk tends to be hard, whereas water running over sandstone or granite for instance, is likely to be soft. Water Hardness Hardness of natural water is caused largely by calcium (Ca) and magnesium (Mg) salts, and to a small extent by iron, aluminium, and other metals. This is referred to as General Hardness (GH), or Total Hardness, and is a measure of all the dissolved salts in the water. General Hardness influences Calcium levels in the blood, and the osmotic regulatory systems of fish are affected by concentrations of dissolved salts. High levels could irritate gill membranes, they may look slightly swollen, and the fish may be seen flicking or rubbing in the water. It is necessary to test for General Hardness so that it matches the original habitat of the species being kept. Hardness is usually expressed in terms of the amount of calcium carbonate (CaCO3 ) present in solution, and is normally measured as parts per million (ppm), or German degrees (ºdH) of hardness. Below is an example expressing soft to very hard:
To convert ppm to the German formula: ºdH……...ppm x
0.056 = ºdH If GH is too high:
If GH is too low:
Carbonate Hardness (KH), or Temporary Hardness is principally composed of bicarbonate ions (HCO3 ) and carbonate ions (CO3 ), and has the capacity to neutralise an acid, this is known as the buffering capacity. Carbonate Hardness stabilises water pH . The immediate aspect of this is that aquariums with soft water are more likely to suffer from the phenomenon known as pH “crash”. This is when the pH abruptly drops, and for the newcomer to the hobby, it would seem like there was no apparent reason. Carbonate Hardness (KH) is expressed in terms of the amount of calcium carbonate (CaCO3 ) present in solution. The test is similar to the GH test, but with a different reagent (the substance used to react with your water in the test tube to obtain a result). A general evaluation is shown below:
If KH drops you can raise it by either:
If KH is too high:
As I’ve just mentioned, this is a general evaluation only, and every fish keeper will have his or her own story to tell. For instance my 4 foot tank:
And my 3 foot tank:
And my Tap water:
You will notice the differences between my Tap water and both tanks, and this is an example of manipulating the chemistry to suit ones needs. The hardness and pH of your tap water supply is the first thing you should evaluate, knowing this will enable you to choose fish that would be suited to your water conditions. Alternatively you will have to adjust the chemistry of your tap water to suit the requirements of the fish that you choose. pH of Water As you may have noticed pH is closely linked to water hardness, generally speaking, a higher concentration of salts means a higher pH , and a lower concentration of salts means a lower pH . The term pH refers to the “power of hydrogen”, and is measured on a logarithmic scale of 0 to 14, pH 0… strongest acid, represents a solution normal in hydrogen ions (H+ ) pH 7… being neither acid nor alkaline, and considered neutral and having equal numbers of hydroxyl and hydrogen ions. pH 14… strongest alkaline, the solution is normal in hydroxyl ions (OH- ) You would need a thorough knowledge of basic chemistry to understand the true meaning of pH in water, and I’m no expert, so for our purpose we will define acidity and alkalinity in terms of the number of ions found in the water. If there is an excess of hydrogen ions (H+ ), then water is said to be acid. If on the other hand there is an excess of the negatively charged hydroxyl ions (OH- ), then the water will be alkaline. Being logarithmic means that a change from pH 7.0 for instance, to pH 6.0 is actually a ten-fold increase in acidity, or, a ten-fold increase in hydrogen ion (H+ ) concentration. To give a more powerful example: pH 8.0 is 100 times more alkaline than pH 6.0, or a 100-fold increase in the negatively charged hydroxyl ion (OH- ). It is necessary to maintain a stable pH , and in the correct range, to keep tropical fish healthy and colourful. As a general guide, egg-laying fish such as:
While the live bearing species such as:
When keeping: Mixed community aquarium a neutral pH of 7.0 would be ideal. Excessively acid or alkaline conditions in the aquarium, as well as pH fluctuations should be avoided, it will cause stress to your fish, and a stressful environment leads to lower resistance to disease, poor fish colour and poor appetite. A minimum pH of 6.5 is sensible; filters are less efficient below this, due to the growth and survival of nitrifying bacteria becoming reduced. Species requiring a pH below 6.5 should have frequent water changes to prevent the accumulation of nitrogenous waste. Any changes made to the pH of aquarium water should be conducted slowly over a number of days to avoid stressing your fish. As mentioned earlier, pH is closely linked to water hardness, if your pH is high then it is probable that your water is high in calcium bicarbonate, and if you remember this is an effective pH buffer, and acts against processes which try to change pH . Having said that, you may recall that my example above shows my tap water at pH 9.0, whereas the GH is only 60ppm, and KH is 10ppm. This is one of the anomalies that exist in this hobby, and it is up to the individual to assess his or her own conditions. For this reason I use a commercial pH adjuster, which sets the pH at a fixed level. It then holds or “buffers” the pH at that level and fights against “ pH rebound” (ordinary adjusters only temporarily change pH , and water can very quickly return to its previous condition, this is known as pH rebound). The product that I use is called PROPER pH TM, it also Neutralises Chlorine, Detoxifies Heavy Metals, adds Electrolytes, and contains Aloe Vera. Therefore added at every water change it does everything I need. The waters hardness can be controlled separately, as outlined previously. Unfortunately, there are a number of naturally occurring processes in the aquarium that can threaten to alter the perfect pH that you have provided for your fish. The filters task of breaking down toxic waste ends in the formation of nitrates, which are a salt of nitric acid, and can exhaust the pH buffer, and cause sudden drops in pH . This can be prevented with regular water changes (which are a part of regular maintenance anyway) that dilute the nitric acid, and are more effective when coupled with a thorough cleaning of any accumulation of debris in the substrate. An effective method against these sudden drops in pH , as I do, is to maintain the pH buffer, with the addition of a pH buffer salt, as I outlined above. Carbon dioxide (CO2) is introduced into the water by the respiration of fish, plants, and other living organisms. When this dissolves in the water it forms carbonic acid (C2CO3 ) and can drop the pH . Aeration: Good aeration and circulation assist in the removal of CO2 into the atmosphere, and reduces its effect on pH . The surface area of an aquarium, as a general rule, should be wider than it is deep; this gives a greater surface area for any given volume of water, which aids this “gassing off”, and is also greatly beneficial for the absorption process. The two elements, hydrogen and oxygen, are chemically bonded together and are not readily freed. Therefore, fish cannot use the oxygen that is in the water molecules. As you may recall, water is capable of dissolving many substances, and oxygen is no exception. Oxygen is constantly being absorbed from the air, by the water surface, and diffuses through it. Fish utilise the dissolved oxygen from the water by means of gills; then excrete their carbon dioxide waste back out through their gills into the water. In this way gills are comparable to lungs. Aerating your water, with either air stones run from
an air pump, or via the venturi of an internal power filter or power
head will help in the process of oxygenation, but not in the way you
might expect. It is a common error to believe that aeration gives oxygen
to the water. The reason for aeration is two-fold; first, it aids the
circulation of water, therefore reducing the possibility “of dead spots”,
and also allows the water to pickup soluble atmospheric oxygen from
the surface (This is why the surface area of your aquarium is so important).
The Nitrogen Cycle: When fish, plants, and food are introduced into the aquarium, a process known as nitrification occurs, referred to as the “nitrogen cycle”. This is not unique to aquaria; nitrification will occur in any body of water, or soil, where bacterial action breaks down decaying organic matter and converts it into ammonia. Ammonia compounds are then oxidized into nitrite and nitrates. These nitrifying bacteria can be termed, as “ beneficial, or friendly bacteria ”, without them aquarium inhabitants could not survive. The process begins with Heterotrophic bacteria consuming fish waste, decaying vegetation, and uneaten food, and converting them into ammonia. Ammonia/Ammonium: Ammonia (NH3) is a colourless, pungent, suffocating gas, a compound of nitrogen and hydrogen, and is very soluble in water. The majority of waste produced by fish is in the form of ammonia, most of which is secreted through the gills. The remainder, excreted as faecal matter, is converted to ammonia by Heterotrophic bacteria. Ammonia is extremely toxic to fish and must be removed or broken down. Visual signs of fish succumbing to this toxicity include:
Because of the toxic effects of high levels of ammonia, there maybe fatalities, even after ammonia levels are brought under control. Smaller fish have a higher gill surface area relative to larger fish; and are therefore more susceptible to ammonia toxicity. Water changes are the best way to solve ammonia problems. You should do partial water changes over a few days, to bring levels down. Resin-based media or Zeolites are available at aquatic shops and are very useful at removing various substances from fresh water aquariums, including ammonia. Moving fish to a “safe tank” will stop the absorption of ammonia immediately, and they can be returned to the main tank when ammonia levels return to zero. If you have a high pH level, you could try reducing it to nearer 7.0, as this will also reduce the ammonia toxicity. pH is an important factor in controlling many chemical balances, of which ammonia and ammonium are included. As I’ve already mentioned pH is logarithmic, and this is the controlling factor over the presence of ammonia or ammonium. Ammonium (NH4) is less toxic than ammonia, and is formed when ammonia reacts with acids, therefore, if ammonia is present in the aquarium, and the pH of the water is acidic, then ammonia will become ammonium. As pH rises, so does the toxicity of ammonia, i.e. a pH increase from 7.0 to 8.0 would be a ten-fold increase in the hydroxyl ion, (and decrease in hydrogen concentration) and ultimately a ten-fold increase in ammonia toxicity. It is therefore necessary to test for ammonia before significantly increasing pH . Nitrite: Ammonia testing will show a zero reading when the nitrogen cycle is working well, and the Nitrosomonas bacteria are consuming the ammonia and converting it into nitrite. Nitrite (NO2) is also toxic to fish if it is not removed, or converted during the nitrogen cycle, into nitrate. Levels above 1ppm need to be removed by carrying out substantial water changes. This should be done on a daily basis for a number of days, testing regularly, until the nitrite level has reduced to zero. Moving the fish to a “safe” tank will stop the absorption of nitrites immediately. They can then be returned to your main tank when nitrite readings show zero. Symptoms of nitrite toxicity include:
Nitrite is also dependent on pH , and if pH drops below 6.5, when nitrite is present in the water, the nitrite will convert to nitrous acid. Which too, is very toxic to fish. Nitrate: Nitrate (NO3) is the end product of the nitrogen cycle, and is relatively non-toxic; although in high concentrations can still be a problem. Nitrite is converted into nitrate by the bacteria Nitrobacter, and the presence of nitrates in a fresh water aquarium indicates that the nitrification process is working. Some species are more tolerant than others to nitrate, but a sensible approach would be to keep levels below 50ppm (mg/l). Some of the symptoms of nitrate toxicity would be:
Nitrates are an essential food source for plants and algae, so if you encourage healthy plant growth in your aquarium, levels will be reduced. Otherwise, if tests show high levels, it would indicate a partial water change is necessary. Regular partial water changes when carried out during maintenance will usually keep it under control anyway. Ammonia and Nitrite levels will tend to be at their highest in the first 4 to 6 weeks of establishing a new aquarium. Because of this you should be aware of " new tank syndrome ". Hydrogen sulphide (H2S) is an extremely poisonous gas that smells like rotten eggs, even in small concentrations it can cause a quick death. It is produced during the decay of organic matter that
contains sulphur, and by the action of dilute acid on the sulphides
(acid aquariums being at risk).
Regular aquarium maintenance, ensuring to clean all debris from the substrate, will prevent the problem arising. Media: This is the plural of medium, and in aquarist terms relates to the passage of water through a suitable material, to have an affect on, or change to the water. In other words, filtration, and without it waste matter would quickly build up and foul the water, turning it into a deadly cocktail of chemicals. Media is classed into three categories: Mechanical - Biological – Chemical, each with its own job to do. A simple example of a filtration system would be: Mechanical Materials like “filter floss" (a synthetic wool), or foam sponge, are very good at removing floating debris from the water, a term referred to as “polishing”. As well as making the water clear, its primary function, when used in multi-chambered filters, is to prevent the “biological media” from clogging. Biological action will occur to a degree on mechanical media as water passes through it. Because of the nature of their job mechanical media
require regular cleaning. Biological, or bacterial media should have lots of surface area to perform well. This is where the microscopic bacteria live, and they take up residence in the millions of tiny holes made available to them in the media. Foam (specifically for aquarium use, non toxic) can be used in this application because of its large surface area, and water easily passes through it supplying the bacterial colony with fresh oxygen and nutrients, indeed, many filters rely on foam as the main medium. There are many products available claiming very high surface areas, such as biotic rock, ceramic media and sintered glass for example. These products are extremely porous, hence the high surface area. If they were to be flattened out they wouldn’t work very well, but the surface area would be huge. Some claim to have surface areas the size of a doubles tennis court from a one-litre pack. Bacteria are very tiny and will colonize anything they can cling to, so enough of anything will act as a medium, even the gravel in your tank. Chemical This is the final stage of filtration, whereby Chemical media will change the waters qualities by reaction, and adsorption. Carbon is the most popular chemical filter medium, and is very good at removing pollutants from freshwater and marine aquaria, or rainwater before it is used in your aquarium. Unlike mechanical media, which can be washed and re-used, or biological media that will last as long as it is colonised by bacteria, carbon will become saturated and have to be renewed. Failure to renew carbon can lead to the pollutants it’s collected breaking down and being released back into the water. phosphates and nitrates can be removed with the use of various resin-based media, while zeolite, another popular chemical filtration media, works by removing ammonia from fresh water aquaria, and releasing less harmful sodium. Unlike carbon, that must be discarded when used up, washing it in salty water can recharge zeolite; this will flush out the ammonia and replace it with more sodium. In order to keep the nitrification process working efficiently, good aquarium hygiene must be observed, which means regular maintenance, keeping gravel clean, removing debris and uneaten food. Above all do not overstock or overfeed, this is inviting problems. The aquarium is an enclosed environment, relying on artificial means to survive, and if the media becomes clogged it will dramatically reduce the surface area available for colonisation, and significantly slow down ammonia and nitrite consumption, which in turn will lead to stress in your fish and outbreaks of disease. |
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