Oxygen is vital to the well-being and overall condition of fish, plants and filter bacteria. Water contains far less oxygen than air, and at times it can become limiting. It is important to check oxygen levels from time to time, particularly at warmer times of the year. The only way to check the oxygen level is with a TetraTest Oxygen test kit.

How it Works
The TetraTest Oxygen kit is a liquid kit, which works by changing the colour of a water sample in relation to the oxygen concentration. You simply need to compare the colour of the sample to the enclosed colour chart, to determine the oxygen level.

How to Use
Take water from below the surface, rather than at the surface. Pour out any excess water, until the water level reaches the 15ml mark.
Hold bottle number 1 upside down and add 5 drops to the test vial, then hold bottle number 2 upside down and add 5 drops.
Press the lid back on and turn the vial upside down and back again once. A sediment will form in the vial.
Leave it to stand for 30 seconds. Remove the lid and hold bottle number 3 upside down, and add 5 drops.
Press the lid back on and turn the vial upside down and back again twice. The sediment dissolves and test solution will turn violet-red. Compare the colour of the sample to the colour chart.

It is advisable to test oxygen levels first thing in the morning, as this is when they are likely to be lowest.