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PH is a measure of the degree of acidity or alkalinity present in your fish tank water.    On the pH scale 0 is the most acidic, 7 ias neutral and 14 is the most alkaline.   Most fish thrive in a pH range of 6.4 to 7.8 but there are 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.  While a fish may prefer a pH of 7.2 it will most likely be perfectly happy with a pH of 6.7.   However that same fish will be really stressed if it has to endure a pH swing of 0.3 in 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 measns that the pH should nt range by any more than 0.2 over 24 hours.

In some cases breeding only takes place at a particular pH value.   You need to research the pH range needed for a particular species to breed in if you want them to breed.    Some species have a very tight range while others are more forgiving.   This is probably the only good reason why you might want to aim for a particular pH value.

Factors Affecting pH

• Biological filtration As you know a good filter system is absolutely necessary in a well stocked tank.   Biological filters reduce pH because they release carbon dioxide into the water.
• 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.   When you water has a kH of above 4.5 it is said to have a good ‘buffering capacity’.

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
This should be done carefully since raising the water pH makes any ammonia in the water more toxic to the 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

It is much more important to have a stable pH than to have a specific value for your 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’.

Adjusting the pH in your aquarium can be dangerous to the fish as swings of just 0.3 in a day can be deadly.   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