pH, Power of Hydrogen: pH: Is the measure of acidity or alkalinity in water. 7.0 is neutral, lower than 7.0 is acidic and higher than 7.0 is alkaline. Proper pH is perhaps the most important factor in a successful aquarium or pond. Correct and constant pH ensures your fish and plants stay healthy. Different types of fish prefer certain water conditions. Here are a few examples with recommended acceptable ranges:  Freshwater Aquarium & Ponds  Saltwater Aquariums 6.8 - 7.4 for Community Tanks 5.8 - 7.4 mostSouth American Cichlids 7.6 - 8.8 most African Cichlids 7.2 - 7.8 Live Bearing Tropical Fish & Goldfish 6.6 - 7.4 Egg Laying Tropical Fish 8.0 - 8.4 is acceptable