Koi, Goldfish & Pond Bacteria Need Oxygen
Page Summary: We depend upon oxygen for our very survival. Few creatures or microorganisms can survive without oxygen. Fish are no different. Unlike us koi or goldfish cannot breath in oxygen directly. These pond fish need to extract oxygen from the water across their gills. This quite simple means that a pond low in oxygen (eg on hot humid days) creates conditions that can be very stressful to the koi or goldfish. But its not just the fish that depend upon dissolved oxygen in the pond water... the pond biofilter cannot function without oxygen in the circulating water. We tend to think only of fish when discussing ponds but it is the biofilters need for oxygen that perhaps that we should be discussing first. All garden fish ponds will benefit from aeration.
Oxygen, Aerating a Pond
Without oxygen, life as we know it would cease to exist. The life of your garden fishpond relies on oxygen in the same way – and it’s not just your koi and gold fish that need oxygen - in fact, your pond contains diverse populations of micro-organisms that require oxygen in high enough concentrations to maintain a stable pond environment. If they are denied oxygen, everything will deteriorate, but if given an oxygen-rich environment via pond aeration, the life in your garden pond will flourish.
What happens when your filter does not receive sufficient oxygen? You might notice a rotten egg odour which is the result of anaerobic conditions.
In these conditions, beneficial filter bacteria aren’t able to oxidise ammonia into nitrite and then into nitrate, causing toxins to build up and become altogether hazardous to your koi and goldfish.
Things to Consider:
The physical make-up of water is different to air, in that we will only find approximately 1% of dissolved oxygen in a natural body of water, as opposed to 21% in the air we breathe.
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Testing pond water can in itself become an intriguing and interesting hobby. Get a reliable test kit however.
The amounts of dissolved oxygen found in water are so minuscule that we measure it in parts per million or milligrams per litre.
Even though we’re working with such small amounts, the more dissolved oxygen you add to your pond the better. Just like a fire is fanned into flame with oxygen, the life of your pond, koi and goldfish will only improve with pond aeration. However, factors such as the presence of additional solutes and water temperature will determine the levels of dissolved oxygen that can be accomplished.
For instance, the presence of salts or pond treatments will influence dissolved oxygen levels negatively, which is all the more reason why you should conduct pond aeration even more enthusiastically when adding treatments. The water temperature also affects the level of dissolved oxygen that can be achieved. Unlike other solutes that dissolve better in warmer water, oxygen is dissolved less readily in warmer water.
How Much Dissolved Oxygen Does a Pond Require?
The more dissolved oxygen, the better! In terms of minimum requirements, koi need comparatively low levels of dissolved oxygen than other species of fish. Koi require approximately 6 milligrams of dissolved oxygen per litre of water compared to trout for instance which need a high level of dissolved oxygen, roughly 11 parts per million.
Youll be amazed at how simple it can be to breed fish with the help of spawning brushes. Youll need one mature female and at least two males.
Put the brushes one above the other at the edge of the pond. Spawning usually occurs in the early morning after a night of flurried activity and can take several hours. Most of the eggs will stick to the brushes which can then be taken out of the pond and put in filtered water of the same temperature. If the eggs are not separated from the adult fish they may be eaten.