Product:
pH is the measure of hydrogen ions. It tells us if our water is acidic or alkaline. On a scale of 0 to 14, pure water has a neutral pH of 7.0. Acidic liquids (such as with citric fruits, tannin water) have a pH of less than 7.0, and alkaline liquids (like green tea and soap) have a pH of more than 7.0.
Most freshwater fish thrive at pH levels between 6.5 to 8.0.

If your aquarium has experienced a pH crash, your fish may show signs of stress, such as frantic swimming, lethargy, rapid breathing, or other erratic behavior.
pH can be lowered by tannins from wood and leaves, by adding peat moss, or by using specific substrates. 

It is good to note though that pH levels in an aquarium tends to change throughout the day. The objective is to maintain a stable pH with as little fluctuations as possible.

Instructions:

• Add 5ml of aquarium water in to the test vial.
• Add 6 drops of the pH reagent to the test vial. Swirl for 5 seconds.
• Place the test vial against the color chart to obtain reading.

Typical pH values for freshwater aquariums should be in the range of 6.5 – 7.5.

Note:
Keep out of the reach of children! Only for aquarium hobby use.
The use of protective gloves and eye protection is recommended.
Please read the instructions carefully before using the product. 

Salifert:
Salifert is a Netherlands base company that produces top of the line test kits as well as tank additives and foods for marine and reef aquariums.
Salifert is well established and popular with hobbyist for their accurate and affordable test kits.