The pH scale is a measure of the degree to which your aquarium’s water is acidic, alkaline, or neutral. The pH scale goes from 0 to 14, 0 being the most acidic, 14 the most alkaline and 7 indicating neutral. Most fish happily tolerate anything 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.
It is changes in pH value that affect your fish much more than the actual pH value. 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 become extremely stressed if you have a pH swing of 0.3 over the course of a day.
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 means no more than a 0.2 change over a 24 hour period.
In some cases breeding only takes place at a particular pH value. 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 is probably the only good reason why you might want to aim for a particular pH value.
Factors Affecting pH
- Biological filtration As everyone knows, good filtration is one of the essentials of a well stocked aquarium. Biological filters reduce pH by releasing carbon dioxide into the aquarium water.
- Carbonate Hardness Carbonate hardness or kH is a measurement of the carbonate hardness of your water. The harder your water i.e. the higher its kH then the better the water is at neutralising acids without a major change in pH. This is known as your water’s ‘buffering capacity’ a good kH is above 4.5.
Adjusting pH
Regular water changes (which you should be doing anyway) is the best way of keeping the pH reasonably level.
As stated above you should acclimatise your fish to live in the ph that you provide but if it is necessary to change the ph for any reason then here’s how.
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
This should not be done lightly since as you raise the pH, you are making the ammonia in the tank more toxic to your fish.
- 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
The particular pH value is not so important, what is important is to have a reasonably constant pH value. To this end you should ensure that the kH of the aquarium water is somewhere around 5-6 dH which means that the water has adequate buffering capacity.
Swings of just 0.3 pH in a day can be deadly to your fish. Unless you have good reason it is best to leave the pH alone unless you have a specific reason for changing it.
For more information on freshwater aquarium pH go to my website www.freshwateraquariumsecretsonline.com
