pH is the measure of acidity or alkalinity of water. A pH reading of 7.0 is neutral, a pH higher than 7.0 is alkaline, and a pH lower than 7.0 is acidic.

Recommended Safe pH Levels

Fish can survive in a pH range from 6.0 to 9.0. In a freshwater aquarium, a slightly acidic pH (6.6 to 7.0) is recommended for egg-laying fish, a slightly alkaline pH (7.2 to 7.6) for live-bearing fish and goldfish, and a neutral pH (7.0) for a community aquarium. Most African Cichlids do well in a pH range of 7.4 to 8.2.

Low pH Caution

A drop in pH can be caused by one or more of the following conditions:
I. Increased carbon dioxide levels resulting from overcrowding, poor oxygenation, or poor surface agitation.
Recommended Action - Increase aeration and surface agitation decrease number of fish.
2. Increased levels of organic materials such as solid fish waste, and particles of decaying plants and uneaten food.
Recommended Action - Clean surface material from gravel bed. Reduce the amount of food given at each feeding. Change activated carbon.

High pH Caution

At a high pH level, (8.0 and above), the ammonia in an aquarium is ten times more toxic than at a 7.0 pH level. If the pH is high the ammonia level should be monitored closely. Use the Freshwater Ammonia Test Kit to determine aquarium ammonia levels.

Avoiding pH Shock

Care should be taken when introducing new fish into an aquarium. To ease the pH change, the water in the fish container should be exchanged slowly with the aquarium water. When introducing new fish, slowly add aquarium water to the fish bag over a 30-minute period of time. When changing the pH of an aquarium in which fish are present, care should be used so that the pH is not changed more than 0.2 in any 24-hour period (for example, from 6.8 to 7.0).