There can be different reasons why fish kills happen in a pond, lake or river system. Two of the main reasons are;
- A major algae bloom that stops oxygen transfer into the water and when the algae die off, the oxygen is stripped from the water and the fish are starved of oxygen resulting in mass fish deaths.
- Another reason is the build-up of organic matter in the bottom of the river or lake. When weather conditions change and mixing occurs through the water column, or there is rain that stirs a river or lake, the deeper water rises to the surface (also called de-stratifying). When this water mixing happens, the organic matter that was at the bottom sucks up oxygen in the water near the surface and the fish die. This is often called a ‘blackwater event’.
There have been major fish kills at various times across Australia, from 2010, 2011, through to 2017 and the extreme event in the Darling River this year.
Preventing these events and improving the health of lakes and rivers is definitely possible, but not if the current approach continues.
Diatomix is an innovative and proven way to improve water quality and is being used to treat many different sites, including lakes, wastewater and aquaculture. In each treated system the nutrient levels reduce and other algae, like blue-green algae reduce markedly in density. The levels of dissolved oxygen also increase and stay consistently higher than an untreated system. With the enhanced oxygen levels the natural biology (micro-organisms) in the water can breakdown the organic matter so that it won’t use up all the oxygen in the water when it gets stirred up. When weather conditions change and the water de-stratifies there will be less reduction in the oxygen levels, and recurrent fish kills will stop.
Before and After Diatomix treatment to improve water quality
It is common for these fish kills and algae blooms to be called ‘natural events’ or natural phenomena’. They occur because naturally occurring algae grow and die, but the intensity and frequency of these events are driven by nutrient pollution and human activities so they are not ‘natural events’ in that regard. This is why we humans, as the creator of the pollution, should be doing more to improve the problem. Relying on rain events to flush away the pollution is not a sustainable solution. With climate change increasing the length of droughts, we have to use new thinking and new methods to address these problems before our lakes and rivers start having so many fish kills that they never recover. Dead rivers help no-one!