Choosing and Conditioning the Water in Your Aquarium
Written by Katherine Barrington
Learn about how to properly choose and condition the water you use in your freshwater aquarium.
The single most important factor in the health of your fish is the quality of your water. Therefore, it is imperative that you choose your water source correctly and condition the water in an appropriate manner. This article will help you address both of these issues.
The majority of freshwater hobbyists simply use their tap water. It is the easiest source to get your water from and in most cases, works just fine. However, the parameters of tap water can vary widely from location to location. You need to test your tap water for pH, gH, kH, and nitrates to understand exactly what is coming out of your tap. If the preferences of your fish are drastically different than your tap water’s parameters, you may need to use a different water source.
Remember to always use a dechlorinator/chloramine remover on your tap water if it comes from a municipal water supply. The tap water is made safe for humans, but not for fish. In fact, it would be pretty much impossible for water companies to make the water safe for fish and humans as the compounds that kill fish (chlorine and chloramines) are a necessity for humans as they kill bacteria and other pathogens.
If you are against using chemicals altogether, another method to remove the chlorine is simply to leave the water sitting out for 24 hours.
One possible alternative to tap water is spring water. Spring water is useful if you need to lower the pH or the hardness of your aquarium’s water. The main drawbacks to spring water are its price (water changes can get fairly expensive especially if you are changing out larger volumes) and the fact that the mineral content varies widely from brand to brand. It is best to buy several different brands in the beginning and test each of them for pH, kH, and gH. Then pick the one that matches the preferences of your fish the closest. One way to find a happy medium between your tap water and spring water is to mix the two. This will also help cut the cost. You will again need to experiment with different mixes to find the right proportions for the parameters you are looking for. Also be sure to check that no harmful colors, flavors, preservatives, vitamins, or additives are added to the water as these can kill your fish. Also make sure that the bottled water is not distilled (a process whereby they cause the water to evaporate via boiling and then cool it back to a liquid state and collect it) as it will lack the trace elements and minerals needed by fish.
Reverse Osmosis Water
Another choice is reverse osmosis water. Reverse osmosis is the process by which pressure is applies to a concentrated solution to force it through a membrane. The membrane will allow the water molecules through, but will block larger molecules such as minerals and other contaminants. There are several membrane types used for reverse osmosis:
● Cellulose Tri-Acetate (CTA) – CTA membranes are made of organic materials and produce less pure (remove 88% - 94% of impurities) water than the other two membranes. They do not get rid of chlorine from the water so you would still need to use a dechlorinator or leave your water sitting out for 24 hours.
● Thin Film Composite (TFC) – TFC membranes are made of synthetic materials and remove 94% - 98% of impurities.
● High Removal Membranes – High Removal Membranes are made of synthetic materials and remove 97.5% - 99% of impurities. These membranes are very good at removing silicates.
One problem with reverse osmosis water in freshwater aquariums is that it may be too pure. It contains practically none of the trace elements required by your fish. Therefore, it is never a good idea to use only reverse osmosis water. Instead, it should be mixed with your tap water in some proportions. You will need to experiment with different proportions to find what gives you the water parameters you need. If you do not want to mix it with tap water, you can add the trace elements back in yourself via some commercial product.
Another problem with reverse osmosis water is that it has zero kH and gH. This means that is has no buffering capacity and is very soft. The result can be huge swings in pH and other water parameters. This obviously is not good for your fish. This is another reason that mixing it with tap water can be useful as the tap water will raise the kH and gH. You could instead add a commercial buffer, but you need to take caution when doing this. If you try to do 100% reverse osmosis water and add chemicals/products to adjust for the problems, you need to carefully monitor all the parameters to make sure you do not crash the aquarium.
Local Lake/River/Creek Water
While it may seem like a good idea to use water from a local source, it usually is not. It will save you money, but it may cost you in other areas. You will usually have no idea what kind of pollutants the water has in it or its mineral content. This can make it very hazardous to your fish. It is for this reason that local lake/river/creek water is not recommended for use in an aquarium.
Rain water is similar to lake/river/creek water in that you do not know what kind of pollutants are in it. The air around you may look clean, but you have no idea what the rain water picked up on its way down. Therefore, rain water should not be used in an aquarium.
Water Parameters and Problems/Solutions
● pH – pH measures whether your water is basic, acidic, or neutral. A pH of zero is the most acidic, 14 is the most basic, and 7 is neutral. Most fish prefer a pH in the range of 6.4 - 7.8, but some fish prefer a pH outside this range (for example, African cichlids prefer a pH higher than this). Despite the fish having preferences for certain pH values, most are able to easily adapt to a wide range. They cannot, however, live through large pH fluctuations (large means fluctuations of greater than 0.3 over a 24 hour period). Therefore, instead of shooting for a specific value, it is much more important to maintain a constant pH.
If you are having problems with your pH, you can read the article on this website entitled Properly Maintaining the pH in a Freshwater Aquarium. You can also try to adjust what water source you use. For example, if your pH is too high, you could try mixing in some spring water to lower it. If you are experiencing large pH swings, it may be because your kH is too low and your water does not have enough buffering capacity. You can measure your kH and then take steps to correct for low kH.
● kH – kH measures the concentration of carbonates and bicarbonates in your water. It also indicates the buffering capacity of your water. Buffering capacity is the ability of your water to neutralize added acid without significantly changing the pH. If your kH is too low (less than 4.5 odH), you may start to have problems with large pH swings. Over time, the nitrates in your aquarium will rise and the pH will drop. Having a high buffering capacity will resist this drop and maintain a stable pH.
If you have low kH, you can add baking soda (will need to be continually added with each water change), increase the aeration in your tank (to drive out the carbon dioxide), or add chemical products (although these usual only fix things temporarily).
If your kH is too high, you can add reverse osmosis or spring water to the tank, inject carbon dioxide, or use chemical products (again, this is only a temporary fix).
● gH – gH is the general hardness of the water. It is mostly a measure of the concentration of magnesium and calcium ions in your water. gH is the parameter that dictates whether you have “hard” or “soft” water. Therefore, if you read that your fish prefers soft water, they mean that your fish prefers a low gH, not a low kH. Like pH, most fish are pretty adaptable to a wide range of values despite their preferences. The biggest exception to this is during breeding for many species.
If your gH is too low, you can add rocks such as limestone to the aquarium or you can use crushed coral as your substrate (or place it in your filter in a mesh bag). These substances will also raise your pH.
If your gH is too high, you can filter through peat moss, add reverse osmosis/spring water, or use a commercial water softener (although this is not generally accepted as safe for many soft-water species as it introduces sodium which many do not tolerate well).
Conditioning Your Water
I am a big believer in adjusting your fish to your water and not the other way around. Therefore, I do not usually advocate the use of chemicals (outside of medicinal purposes) except for a dechlorinator/chloramine remover. There are many commercial products on the market today that allow you to remove such and such material from your water or fine tune some parameter. I find that natural solutions tend to work best. If you need to lower the pH, put some driftwood in the tank. If you need to harden your water, put a bag of crushed coral in the filter. If you need to lower the kH, mix your tap water with some reverse osmosis/spring water. All of these methods are easy to duplicate and repeat for years. On the other hand, trying to figure out how multiple chemicals react to each other and to your tank can be close to impossible. Therefore, I advocate always looking for natural solutions before turning to chemical ones.
In an effort to save people money, do not buy products that advocate being a general water conditioner or a bacteria supplement. If you have cycled your tank then you are already an expert at growing bacteria and do not need help from a bottle. Instead of the general water conditioners, just buy a normal dechlorinator/chloramine remover.
Tap water is usually your best water source. However, some people live in places that have terrible water quality (or water parameters that do not mesh well with the preferences of their fish). If this is the case then the addition of reverse osmosis or spring water to tap water can help. Rain water and water from local lakes/rivers/creeks is never recommended for use in an aquarium.
For additional information, refer to the following web pages:
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