In Part 1 of this two-part article you'll discover some of the reasons why pH levels can drop in your aquarium and what you can do about it.
If you have done any research about maintaining a healthy freshwater tank, you have probably read a great deal about pH and its effect on tank inhabitants. Not only does the pH level of your tank affect the water quality, but it can also have an impact on the health and vitality of your fish. Many novice aquarium hobbyists experience problems with low pH or a sudden drop in pH in their tanks and, when this happens, they are at a loss what to do. If you are experiencing pH problems in your tank, it is wise to first identify the cause of the problem and to make the necessary corrections before taking steps to adjust the pH back to a normal level.
The Basics about Aquarium pH
The pH of your aquarium is simply a measure of how acidic or alkaline your tank water is and it is measured on a scale from 1 to 14. A pH value of 7.0 is neutral while values below 7.0 are considered acidic and values above 7.0 are considered alkaline. Most species of aquarium fish can tolerate a pH range from 6.5 to 7.5 but certain species like some cichlids are very sensitive to changes in pH and require a certain, stable level. Before you set up your tank for the first time it is wise to test the pH of the tap water you intend to use to fill your tank. The pH of your tap water may vary according to where you live and, depending on the species of fish you plan to keep, you may need to make adjustments to reach the ideal pH level in your tank. Once you have established the proper pH it is a good idea to monitor it with weekly water tests so you can catch any changes in pH before they become a major problem. It is not uncommon for aquariums to suffer a change or drop in pH and the sooner you take action to correct it, the less likely it will be to have a negative effect on your fish.
Causes for a Drop in pH
You already know that low pH values (values below 7.0) are considered acidic, so it makes sense that the pH level in your tank will drop following the addition of acids. Extra acid can make its way into your tank through several means -- some are naturally occurring and some may be the result of a mistake on your part. Some of the naturally occurring causes of a pH drop include excess carbon dioxide, tannins from driftwood and the nitrification stage of biological filtration. Carbon dioxide (CO2) is the natural product of respiration, so the more fish you have in your tank the higher your CO2 levels are likely to be. The decay of plant matter can also increase the CO2 levels in a tank and many biofilters actually produce carbon dioxide. The best way to counteract high CO2 levels is to ensure that you have plenty of live plants in your tank – live aquarium plants utilize CO2 in the process of photosynthesis, using light as an energy source to convert CO2 into oxygen for respiration.
Another possible cause for a drop in pH is the leaching of tannins from driftwood or leaf litter. Driftwood is often used for décor in the aquarium trade because it provides cover for fish while enhancing the “natural” appearance of the tank. If you do not properly treat your driftwood before adding it to the tank, however, it can cause problems with your water chemistry. Driftwood contains tannins, or tannic acid, a natural compound occurring that stains water yellow or brown – tannins are responsible for creating “blackwater” habitats like the Amazon River. To prevent tannins from affecting your water chemistry, boil the driftwood or soak it for a period of several weeks before adding it to the tank. Boiling and soaking driftwood will help facilitate the release of the tannins, thus decreasing the chance that the driftwood will cause a pH drop in your tank.
In addition to excess carbon dioxide and tannins in the water, a pH drop may also be caused by the nitrification stage of biological filtration. Nitrification is the process through which beneficial bacteria in the aquarium convert ammonia to nitrite and then into nitrate. Ammonia is a substance toxic to fish, so the process of converting it into nitrate is extremely important for maintaining a healthy tank. During this process, however, your tank may experience a natural drop in pH as a result of the production of nitrite ions. Once your tank has properly cycled, however, it should establish a balance capable of counteracting this drop in pH to keep the water chemistry stable for your tank inhabitants.
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