How Much Oxygen Do Fish Need?

All Pond Life Needs Oxygen
Not only do these organisms demand oxygen, they must receive it insufficiently high concentrations so that the function and health of the pond is maintained. Diverse populations of micro-organisms as well as fish rely on a supply of oxygen.

Deny them oxygen, and the water quality will deteriorate; add extra and the pond will explode into life.

Without oxygen, filter bacteria cannot oxidise (and detoxify) ammonia into nitrite and then into nitrate. If a pond or filter are allowed to become oxygen deficient for any period of time, anaerobic conditions will prevail causing unstable water conditions and the tell-tale bad-egg smell.

So how do we best use those devices that are available to us as fish keepers to add extra oxygen into our demanding ponds? How do they work, and how can we measure how efficient and effective we are at adding extra aeration?

Disolving Oxygen Into Pond Water
The physical nature of water puts limitations on how much oxygen we can expect our pond water to hold. It also sets targets for what we should expect to achieve under different pond conditions. In the air we breathe, there is approximately 21% oxygen (210,00ppm oxygen).

In any natural water body, we will typically find less than 1% dissolved oxygen. So tiny are the concentrations of dissolved oxygen in pond water, that their levels are measured in milligrams per litre or parts per million (ppm). For example 3 milligrams of oxygen dissolved in a litre of water equates to 3 ppm.

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