[Myka]

Putting tank water into a container, travelling with it for a time, then testing it later on is absolutely not an accurate measurement of your tank's dissolved oxygen level. You have to take your tank water out, and test it within a few minutes of removing it from the tank in order to get an accurate test as shaking the water a bit will increase the dissolved oxygen content, and letting it sit will lower the dissolved oxygen content, even in a sealed container. Don't consider that test your be all end all, it has very little bearing. I am surprised the employees at AA didn't know that or failed to express it to you. It's kind of silly they would even test customer's O2 levels from the store since their readings would never be accurate.