sera Oxygen Test

The sera Oxygen Test (O2) is a quick, accurate reagent test for measuring the dissolved oxygen level in your aquarium or pond, in both freshwater and saltwater. Dissolved oxygen is essential for fish, invertebrates, and the beneficial bacteria in your filter, yet it is one of the most overlooked water parameters. This kit lets you confirm your tank is well oxygenated and catch problems before they stress or harm livestock. Pair it with the rest of our water test kits.

Why test oxygen

Oxygen keeps fish breathing, powers your biological filter, and supports healthy invertebrates and plants. Levels fall with higher temperatures, heavy stocking, overfeeding, at night when plants respire, and when surface agitation is low. A low reading is an early warning to increase aeration or circulation before your livestock suffer.

How to use

• Rinse the test vial with the water to be tested
• Add the sera reagents exactly as directed in the instructions
• Compare the resulting color against the sera color chart to read your dissolved oxygen level
• Increase aeration or surface movement if the reading is low, then retest

Follow the included sera instructions for exact drop counts and timing. Suitable for freshwater and marine aquariums and ponds.

Specifications

Frequently Asked Questions

Why does dissolved oxygen matter? Fish, invertebrates, and filter bacteria all need oxygen. Low levels cause stress, gasping at the surface, and can be fatal, so it is worth checking.

Does it work in both fresh and saltwater? Yes, the sera Oxygen Test is suitable for freshwater and marine aquariums and ponds.

How do I raise low oxygen? Add aeration, increase surface agitation and circulation, avoid overstocking and overfeeding, and keep temperatures in range.

How often should I test? Test regularly, and any time fish gasp at the surface, after adding livestock, or during warm weather.