Household pH levels - hard water, softened water

What is pH?


It's a measure of the acidity or alkalinity of water soluble substances. pH stands for 'potential of Hydrogen'.


A pH value is a number from 1 to 14 with 7 as the middle neutral point. Values below 7 indicate acidity, with 1 being the most acidic. Values above 7 indicate alkalinity, with 14 being the most alkaline. Water suitable for fish can range from pH 6.0 (soft) to pH 8.5 (hard)

Determining the pH level of your aquarium water can help you decide which fish are more suitable for your fish tank, and allow you to provide the habitat best suited to your chosen species.



Your Tap Water

Most tap water in the United Kingdom is moderately hard - with a pH around 7.5 to 8.0

However, household water softeners can reduce the hardening mineral content in your water which attributes to a higher pH level. The result is a lowered pH level, or "soft" water. Typical pH in a house with a water softener fitted is around 6 to 7.

Hard water (high mineral content) is usually high in pH. Soft water (low mineral) is usually low in pH. The mineral in hard water will act as a buffer which will reduce the amount of acid in the water. The resulting water will be more alkaline and higher in pH 6.0.

Certain fish, like neon and rummy nose tetra, prefer a softer water (ph 6.5-7) whereas the vast majority of ornamental tropical fish tolerate neutral to slightly hard water (ph 7-8)

Our tropical fish are stored at a moderately alkaline pH, which will be similar to most tap water in the UK, typically pH 7.2 to 8.0. If you have a water softener, going for fish more tolerant to a low pH is a good idea. Please take care acclimatising if your household pH is significantly different to the recommended perameters. Purchasing an additive to raise or buffer the pH in your aquarium water is also a good idea.

A saltwater aquarium should generally be kept at a pH between 7.6 and 8.4, but the specific pH recommended for your tank may depend on the species you have in the tank. If you are keeping a reef tank, the recommended pH level may actually be higher – between 8.0 and 8.4. You can purchase an additive to help achieve higher pH levels by clicking here.


Each live fish listed on our website will have a recommended pH level in the description. Please contact us if you are unsure of anything in relation to pH.


You can test your water pH level using a basic strip test kit. Click here.


You can buffer or raise pH levels by using an additive. Click here.