Every aerator should be sold with an O2 meter. If you figure 7 cents a kilowatt-hour, a one horse aerator running day and night will cost in the neighborhood of $50/month to operate. Not every pond is going to be a hypereutrophic hatchery raceway posing as a real pond, so some pond owners would be wasting money by aerating during clear weather. It's not worth second guessing your O2 levels at depth. Just get a very basic O2 meter and aerate accordingly.

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