Water Oxygen Content

[Kernel]

Just wondering how you would go about testing a tanks water for its oxygen content? Also what level would you be looking at and how do you control it?

 

[Bignose]

There are dissolved oxygen tests just like ammonia/nitrite/nitrate/GH/KH/pH/phosphate/etc test exist.

But, unless there are some very odd circumstances, the oxygen level is going to be very close to 100% saturation. There isn't much to "control" it -- it isn't a variable to be directly controlled. But, the oxygen level is usually plenty sufficient for fish. Are you having a specific problem?