Dissolved Oxygen

Dissolved oxygen is the amount of oxygen in the water. To do a dissolved oxygen test, first take the "special cylinder", as Ms Wind put it, and fill it with 25 mL of water from your tank. Next, take one of the glass tubes that's filled with a straw color yellow. Next, place it in the cylinder, breaking the tip off. Let it sit in the water for a few seconds before removing it. Then, place your finger over the opening, covering it and gently swish is around. then, let it sit for about two minutes. Lastly, compare your results with the chart. If the level is below 3 mg/L, there isn't enough dissolved oxygen and your fish will die. Anything over 5 mg/L can support life and is a good dissolved oxygen test result. My results were 10 mg/L which is good. In a small pond, the dissolved oxygen is probably lower than in a large river because a pond is usually warmer which holds less dissolved oxygen and fast moving water is more air rated, allowing for more dissolved oxygen.


The darker the blue, the more dissolved oxygen there is.