With the dry season, there’s reduced flushing/dilution of waterways. In fact, in many water bodies, there is increased evaporation, causing concentration of nutrients that algae love.
This creates a nasty looking pond or lake. Based on basic principles, here are possible options for controlling algae:
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Prevent further nutrients from entering the lake – deviating run off, encouraging more marginal plant growth;
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Diluting the nutrients by flushing with water;
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Locking up the nutrients with PhosLock or similar compound;
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Dredging/vacuuming the bottom of the lake to remove nutrients;
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Seed the water body with other algae that can out compete the toxic algae;
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Stock lake with herbivorous organisms that will eat the algae (and in turn be eaten by larger fauna and hence remove nutrients) – e.g. rotifers, brine shrimp, fish (e.g. grass carp, but this is not in Australia);
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Apply algaecides – natural (barley straw or its extract, grapefruit seed extract) or chemical (e.g. simazine, Diazinon, Endosulfan, Propiconazole, Thiram, Ziram, Quinomanid, Irgarol-1051 and Hydrogen peroxide) – check safety for aquatic organisms where present ;
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Limit light entering the system – e.g. putting dyes in the water, providing more shade;
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Allowing the lake to dry out (in fish-less ornamental ponds).
