extreme weather and garden ponds

You will probably have heard the met office's augers of doom regarding extreme weather events. Climate change is causing the UK to suffer a greater incidence of extreme weather. Hail showers in July, a summer heatwave, the Beast from the East and Storm Ali are amongst the freak events that you may have experienced over the last couple of years.

Extreme weather is always an inconvenience and sometimes incredibly disruptive. It is also problematic for ponds. With hotter days and tropical nights becoming more common, pond keepers face greater challenges.

Garden ponds and hot summers

2018 brought us a scorching summer with surprisingly high temperatures for several months. While considerable heat is required to raise water temperature significantly, hot weather will heat up your pond to some degree. Climate change has caused a rise in the average temperatures of freshwater features including ponds and lakes. Warm water can hold less oxygen than cold water. But when the water is warmer, fish require more oxygen due to a rise in their metabolic rates. Freakishly hot weather creates a potentially hazardous situation.

In the summer months, it is vital to ensure that your pond water is sufficiently aerated via fountains, waterfalls or an air pump. Fish gasping at the surface of the water or congregating around filter outlets are signs that they are experiencing oxygen distress. A testing kit will reveal the oxygen levels in the water and would be a good investment.

An oxygen testing kit enables you to react to an issue before it becomes a disaster. It's always wise to remain ahead of the game.

The trouble with shallow water

Shallow ponds are the most prone to raised water temperatures in hot weather and therefore a reduction in dissolved oxygen. Ponds for goldfish should be at least 1m deep and koi ponds at least 1. 7m deep to ensure that the water temperature does not become untenable. Oxygenating weeds won't solve the problem as they only release oxygen during the daylight hours.

To make matters worse, the bacteria which colonise your biofilter are also dependant on dissolved oxygen. If your bacteria fail to thrive, you will be creating a potentially toxic environment. Test your ammonia and nitrate levels regularly as any rise in concentrations could be a sign that the bacteria are struggling. If you run into trouble, boost your biological filtration with active bacteria.

Cold weather blues

Extreme cold brings with it further issues for ponds. Oxygenation is unlikely to be a problem but aerating devices that are still running could be cooling the water too much. The water will hold a higher level of dissolved oxygen in conditions when the fish require less. If you switch off aerating devices, always monitor your water and your fish for oxygen distress.

Providing your pond is deep enough, profound temperature changes are unlikely but even subtle changes can tip the balance and lead to fish becoming distressed. In extreme weather conditions, it becomes harder to maintain the right level of oxygenation and to ensure that the water quality remains optimal.

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