PH measures the degree of acidity or alkalinity present in the water of your aquarium. On the pH scale 0 is the most acidic, 7 ias neutral and 14 is the most alkaline. The majority of fish will happily live in water of pH between 6.4 and 7.8 but there are some exceptions.
pH is a logarithmic scale, in simple terms this means that a small change in value indicates a very large change in acidity or alkalinity.
Changes in pH are much more significant than actual pH values. Even though the books say that a fish prefers a pH of 7.1 it will probably be fine in a pH of 6.6. However the same fish will be most unhappy if over the course of a day it experiences a change in pH of 0.3.
Most aquarists deal with the pH issue by keeping it as constant as possible and getting their fish used to living in that environment. Constant measns that the pH should nt range by any more than 0.2 over 24 hours.
As a side note, some species are very particular about the pH when they breed. If you plan to breed a certain species, research the range of pH it finds acceptable to breed in. Some species are very forgiving, while others have a very tight range. This may be one of the only reasons you need to go for a specific pH.
Factors Affecting pH
- Biological filtration As you know a good filter system is absolutely necessary in a well stocked tank. Biological filtration tends to release carbon dioxide into the aquarium water and thereby reduces pH.
- Carbonate Hardness Carbonate hardness or kH is a measurement of the carbonate hardness of your water. The harder your water is (high kH) then the better it is at neutralising added acids without changing its pH very much. It is called your water’s ‘buffering capacity’, generally speaking, kH should be above 4.5.
Adjusting pH
Frequent water changes (which you should be doing anyway) are the best way to keep the pH up to an appropriate level.
Generally speaking your fish should be acclimatised to the pH you provide but it can be changed as shown below.
How to Lower the pH
- Filtering water over peat
- Add bogwood to the tank
- Inject carbon dioxide CO2
- Use a commercial acid buffer
- Water changes with softened water or RO/DI (Reverse Osmosis/De-Ionized) water
How to Raise the pH
Raising the pH makes the ammonia in the water more toxic to your fish so this should be done with great care.
- Aerate the water, to drive off excess carbon dioxide (CO2)
- Filter over coral or limestone
- Add rocks containing limestone to the tank or use a coral sand substrate
- Use a commercial alkaline buffer
Conclusion
Rather than aim for a specific pH value you should take steps to ensure a stable pH. To obtain a reasonably stable pH the carbonate hardness should be about 5-6 dH so that the water has a reasonable ‘buffering capacity’.
Even small swings of more than 0.2 pH in a day can cause your fish to die. Therefore, unless you have a specific reason for doing so, it is better to acclimate the fish to your tap water’s pH than to adjust your pH to fit the so called preference of your fish.
For more information on freshwater aquarium pH go to my website www.freshwateraquariumsecretsonline.com