Fish Tank pH

What pH should my fish tank be at?

The pH of fish tank water is a common concern for many freshwater fish keepers. As a general guide, most freshwater fish are happiest at around a pH of 7. However, there are some species which have evolved to require a pH higher than this (such as cichlids) and some which are happier at a pH a lower than this (such as discus). Of primary importance for most community tanks is the stability of the pH over time with fluctuations in pH (often caused by the breakdown of organic matter in the tank for instance) being of greater concern that the overall pH.

The way the pH scale is worked out means that a small change in pH is actually quite a large and dramatic change in environment for your fish and these changes are what can be most troublesome for your fish.

The kH of your water is what determines how stable the pH is in your water. Soft water (such as rainwater or reverse osmosis water) has a very low kH which means that tanks primarly composed of this water are going to be more susceptible to pH fluctuations. This water is also said to have a low buffering capacity (because it cannot buffer pH change very well).

The easiest way to monitor the pH (and kH and gH) of your water is to use test strips such as Tetra EasyStrips. There are other testing methods also such as liquid test kits or handheld testing meters. When testing you are most concerned with changes in pH over time (unless the species you have is particularly fussy about a specific pH). pH changes can be managed via water changes (effective if a build up of nitrates/nitrites is what is causing the pH change) or by also adjusting the buffering capacity of your water (ie adjusting the the kH) of your water initially so that it is more resilient to pH changes.

Increasing the buffering capacity of your water can be achieved by using products such as Continuum flora.viv Reconstitute RO powder which has been designed to remineralise water produced via reverse osmosis or distillation (and thus also rainwater). This can be used at initial aquarium setup, or when doing water changes. Once you have used this product you would then test your water again and if further adjustment to kH is required you can utilise Continuum flora.viv KH+ Powder.

It is crucial that any changes to kH and pH should be made gradually to your tank and closely monitored via testing.

A final note is that knowing what water you have available prior to setting up an aquarium can be most ideal. That way you can select species of fish that will thrive with the natural water parameters you have available in your area. Once you start needing to adjust water parameters via chemical means, it becomes a lot more complicated (which is fine if you are a devoted hobbiest with the time and inclination to devote yourself to the education required!).