How to Understand & Test Aquarium Water Quality
People are often afraid of water chemistry, but in reality, water chemistry is easy to understand and easy to test. By taking the time to understand what’s involved, you’ll find fish keeping more entertaining.
It is sometimes said that fishkeeping is not so much about caring for the fish, but caring for the water. In other words, fish depend entirely on their aquatic environment for their health and well-being, and fish thrive by ensuring that the water is adequately filtered, ventilated and kept at the proper temperature.
Basic Principles
A fish living in water is much similar to us being surrounded by air. If there is smoke and toxic fumes in our air, our breathing and life become quite uncomfortable. The same is true for fish living in polluted water. Although we can see smoke in our air, we would assume that the aquatic equivalent would be cloudy water. It is understandable then to believe the misconception that water quality is acceptable if the water is clear.
Many chemicals are transparent, including strong acids, bleach and white spirit, but are very dangerous when ingested. Similarly, the pollution that a fish may experience is invisible to our eyes.
pH
The concept of pH is familiar to many, but it is important to understand that this parameter has some unusual features. The pH of a liquid indicates how acidic or alkaline it is. A neutral substance has a pH of 7, acidic substances have a pH below 7, and alkaline substances have a pH above 7. The farther from this neutral point, the stronger the acid or alkali.
However, the pH scale is not a simple scale. For each unit of pH change, the strength of the acid or alkali changes tenfold. For e.g. pH 4 is ten times more acidic than pH 5 and pH 6 is 100 times more acidic!
This is important because fish comes from all over the world; some from acidic water and some from alkaline water. Putting a fish initially from acidic waters into alkaline waters appropriate for other fish, it may experience a 1,000 times difference in pH from what it is used to.
Nitrogen
About 78% of the air that we breathe is made up of nitrogen gas. However, nitrogen also exists in different forms. Nitrogen is the fourth most abundant element in the body of a fish. It can be found in the protein that makes up muscles, to the DNA exist in every single cell in the body. Fish get all of their nitrogen requirements by consuming plant and animal substance, digesting it and integrating it into their own tissues.
This process is effective, but like many biological processes, harmful waste products are produced. Ammonia (NH3) is one of these nitrogen-based waste products. Many wastes produced by organisms are toxic and must be eliminated from the body. In fish, this waste product is mainly released through the gills.
In their natural environment, the consequence of ammonia is irrelevant. The sheer amount of water rapidly dissolves any such ammonia to low concentrations. However, in captivity, the amount of water contained in an aquarium is limited. Without additional tools, the concentration of ammonia would rise rapidly.
Biological Filtration
In an established, healthy aquarium, ammonia causes little threat. Ammonia is much more of a threat in newly setup aquariums or over-stocked aquariums.
In a fresh new aquarium with fish, ammonia will start to rise. Over time, ‘friendly’ bacterial colonies form on all available surfaces (including the media inside the filter). These bacteria, together known as Nitrosomonas, are able to use ammonia as a foundation of energy. Once again, this process is not without related waste products. Instead, these bacteria convert ammonia into nitrite (NO2). Similarly, this chemical is also poisonous to fish.
Lastly, an additional group of ‘friendly’ bacteria, known as Nitrobacter, are able to consume nitrite as an energy source. Their waste product is one more chemical known as nitrate (NO3). This chemical is comparatively non-toxic to fish. It is watered down by partial water changes or taken up by plants and algae that create their own proteins.
This finishes the cycle by re-entering the food chain where it may once again be ingested by fish.
Oxygen
Oxygen is one of the most significant chemicals to life. While ample in atmospheric air (about 21% of the air we breathe), its availability in water is much lower. Not only is oxygen essential for fish, it is also consumed by the beneficial bacteria that eliminate the fish wastes.
Just as with pH, fish also have different requirements for oxygen. Some fish originating from fast flowing rivers have high oxygen desires, but some fish have altered to low oxygen levels. Such fish may have unique adaptations to manage with low oxygen, such as the capability to breathe atmospheric air.
Salinity
About 71% of the Earth’s surface is covered by water, most of which is oceans.
The average salinity of seawater is about 35 grams of salt per liter of water. However, the salinity is not constant across the world. Some oceans have a higher salinity, such as the Red Sea, while the salinity of the Baltic Sea is less than half of the global average.
In a marine aquarium, there is one main process that causes a variation in salinity; evaporation. The temperature of the water combined with the warmth from the lights leads to water molecules changing from liquid to a vapor. It lags behind all minerals and salts. If this water is not replaced, the salinity will increase, which will adversely affect the fish.
Hardness
While ample in seawater, freshwater can have different amounts of minerals such as calcium and magnesium. Many people know what kind of water is in their area. Rapid accumulation in kettles is usually a clear indication of a hard water area. Other signs include the ease of generating a foam when using soap.
Rivers and lakes around the world vary considerably. The Rift Valley lakes in East Africa are known for their hard water, while the black water rivers in South America are much softer. The fish found in these environments have evolved over thousands of generations and adapted to these aquatic conditions. Similarly, the placement of species from one water to another can adversely affect the fish. However, some species are adaptable and more robust, and may adapt to different types of water quality. It is possible to handle the hardness of the water, which can be considered when choosing fish.
Water Testing
Determining the quality of aquarium water is easy. You can buy test kits that measure most of all the parameters mentioned.
The test kits are available in liquid, tablet and strip forms. The liquid test kit works by adding a particular number of drops to a measured sample of aquarium water. The sample changes colour, which can then be related to a chart to analyze the result. Although tablet tests are very similar, use tablets rather than liquid drops. Strips are also available where the strip is plunged into the aquarium before relating to the colour chart.
Testing the salinity is carried out with the use of a different method. A tool known as a hydrometer is either set within the aquarium or filled with aquarium water depending on the style. It should be remembered that these tools really measure the specific gravity (or SG for short). This intently approximates the real salinity. For an extra accurate measure, the SG and temperature can be used to check the salinity from a chart frequently provided with hydrometers.
To gain more precision and accuracy in the results, an additional testing tool is available. Electronic pH probes can measure pH to a higher level of degree and precision, and controllers can also be received to regulate the pH. These are very useful while using carbon dioxide fertilization in heavily planted aquaria.
In addition to hydrometers, refractometers can also be used to measure salinity. These tools are simple to use and can give a greater level of precision for determining salinity.
Precautions
Chemicals used to test water quality are dangerous to health. Always be careful when using these kits and make sure they do not come into contact with your livestock. Be careful when inspecting to prevent leaks and contact with children and other pets.
Always follow the manufacturer’s guidelines carefully. Many colour-based test kits need a particular amount of time to elapse before comparing to the given colour chart. Confirm you followed the instructions fully to ensure that your testing is precise. Also note that some of the chemicals used cannot be kept forever and may lead to incorrect test results if used outside of this period.
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