Facts: H2O – Oxygen in your Pond

You know that your pond needs oxygen in the water but do you know how much and how often?

Oxygenation is the process in which oxygen is diffused into the water. This process happens every time your water comes into contact with the air.

If there is no aeration in a pond, the pond cannot exchange gasses at the deeper levels of the pond and can only exchange gases at the water surface and therefore, will support only a few fish. Ponds deeper than 3 feet will benefit from a bottom aerator in the summer, especially if this pond is a koi pond.

A pond needs to absorb oxygen from the air and it also needs to release carbon dioxide and hydrogen sulfide among other gases.

Hydrogen sulfide is one of these gasses that contribute to breaking down organic matter in the bottom of the pond. The pond bottom has less oxygen than the upper layers of a pond.

When you use a biological filter or a fountain or have a stream, you increase the surface that is exposed to the atmosphere. Harmful gasses can be released and oxygen absorbed.

Is something wrong with my fish when they swim up near the waterfall and roll around in the area?

They are getting oxygen created by the bubbles that generated from the waterfall. This is a fix of higher concentrated oxygenated water.

But on the other hand, if you see your fish “gasping for air” at the water’s surface, “they may be lacking enough oxygen in the water”.

What is the role of plants in the oxygen supply to a pond?

Plants should only cover 50% to 60% of your pond surface. If you have too many plants in a pond and the entire surface is covered you will have very little gas exchange unless you have a very large waterfall and/or stream.

Adding submergible oxygenator plants (such as Anacharis or Hornwort) will add oxygen to the water but while they add oxygen during the daylight, they use up the available oxygen at night the same as other plant life in the pond.

Anacharis is an important submergible plant as it uses up nutrients that starve out the algae. Go to planning your pond to see how many Anacharis plants you need for your size pond.

Rarely does one overstock with oxygenators, but if in the morning you see your fish gasping for air, you may need to remove some of your oxygenators. The oxygenators may be taking too much of the oxygen over night. Removing too many at once is not good either since it may upset the balance of your pond.  Remember plants remove the oxygen in the pond at night.

Oxygenators are the utility player in the roster of pond plants as they serve as a natural filter, a hiding place for fish, an algal combatant and they look good while doing it all.

Suggested oxygenators: Anacharis, Hornwort, Cabomba,  Parrot Feather, and Mosiac Plant. The submerged ones create the most oxygen.

How do fish enter into the oxygen issue?

There is a limit to the number of fish that you can keep in a pond before you compromise the quality of your pond water.  When you exceed this number you start having problems with water quality and fish health. Usually it is recommended to have 1 inch of fish (mature size) per 1 square foot of surface area of your pond. Stock lighter in the beginning and gradually add more fish but never stocking more than 1.5 inches to 1 square foot.

How does the temperature of my pond water affect the oxygen supply?

The hotter the water the less oxygen it can hold, therefore cold water holds much more oxygen. Using a small bubbler or aerator adds enough oxygen for most size ponds in the winter. Fish do not require a lot of oxygen in the winter because of hibernation.  Warm water has a low capacity for holding oxygen, while cooler water can hold gigantic amounts of oxygen. Warm water and increased activity go hand and hand, and that increased activity means fish require more oxygen.

Stressed fish often begin to develop diseases. If you live in a very warm climate, you might consider stocking with more tropical fish like the swordtail or tilapia rather than coldwater fish.

Also if you live in a hot zone, it is sometimes advised to do a partial water exchange when you water temperature gets high (over 80 degrees). Don’t forget to dechlorinator or use a water conditioner for any city water. You can also add an additional bubbler that will increase the oxygen level of your pond.

To keep your oxygen flow at a healthy level, you need to keep a watch on the amount of plants and fish in your pond. Plants should cover no more than 60% of your pond. Remember fish will produce more fish so start with fewer fish in the beginning.

If you ever have to shut down your pump for any length of time, aeration is vitally important for the life of your fish. In hot weather, your fish could be in danger with a pump failure. It is always wise to keep a bubbler or aerator on hand just in case. In very hot climates where the water is very warm, fish can die within a few hours without oxygen.AquaForce^TM Solids Handling Pump. This pump has a three year warranty and can be used for winterizing or in hot weather to provide additional oxygen to the fish. Comes in two sizes 1000 GPH, and 2000 GPH. And best of all it cost between $3.65 to $8.03 to run.

A back up pump is always a good thing to have.
A good recommendation is the

Call customer service at 877 780-1174 if you have questions.

Happy Pondering,
Aquascapes.com