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Aussie Green Thumb – Top Gardening Tips For Everyday People

Pond Algae – A Growing Problem

Pond algae is a common complaint among pond-owners, and whilst green sludge is the stuff of nightmares, a totally algae-free pond will always be a pipedream.  Because the truth is, there’s no such thing as an algae-free pond.

That’s because algae occurs naturally in water and it’s actually essential for a healthy and ecologically balanced pond.   But whilst every pond will have some algae growing in it, it doesn’t mean that you have to settle for dark, thick and unsightly garden water features.  With regular maintenance and attention, pond algae can be kept under control and to a minimum.

If you prefer clean to green, there are some basic algae facts that you should know which will help with maintenance and planning.   Perhaps the most important thing to understand about controlling the growth of algae is why it grows.  Once you understand what type of environment is conducive to the growth of algae, it will be much easier to know what to do in order to control it.

Basically, algae needs light and nutrients (nitrates and phosphate) to thrive.  It loves a pond where there’s debris at the bottom which results in loads of nutrients. It also loves food, so it’s particularly happy when your fish are being over-fed or your water lilies are getting a bit too much fertiliser.  It likes shallow water where the temperatures are warmer and it loves flat surfaces.  Most of all, algae likes it when the complex system in your pond is imbalanced, so to keep the green stuff in abeyance, the trick is to do the things that restore equilibrium.

Here’s a brief synopsis of what algae likes – and what to do about it:


Don’t overfeed fish or overstock your pond with fish as their excrement may be resulting in excess nutrients.  Some experts even recommend reducing fish food during an algal bloom to force the fish to eat algae instead of their regular food. Check the run-off from gardens, lawns and even aquatic plants to make sure that fertilisers and chemicals aren’t ending up in your pond.


Increasing coverage of the pond’s surface area with floating plants and water lilies will decrease the amount of sunlight available to algae.


Algae will grow rapidly in a small, shallow pond where the water heats up quickly.  Again, lots of lilies and aquatic plants will help shade the water and keep the temperature down.   However, you will notice that algae is generally at its worst in spring when water temperatures are on the rise, the sun is warmer and the plants haven’t started their new season growth.


Excessive surface vegetation can also result in too little oxygen in the water however, and this is detrimental to the growth of algae-eaters such as fish, aquatic snails and tadpoles.

As you can see, keeping a pond healthy is all about balancing the ecosystem and keeping algae to a minimum does require an understanding hand.

But there are some types of algae that don’t need to be treated with any compassion – such as floating and string algae – which are also generally more of a problem during seasonal changes.  Getting rid of string algae requires some manual labour, and is best removed by twirling it around a stick or special pond wand.

There are also many handy pond supplies on the market which are very helpful in keeping algae to a minimum.  For example, an aerator will oxygenate the water whilst a vacuum can remove organic waste or sludge from the bottom of the pond, thereby preventing algae.

Water treatment products are also very helpful, and Clearpond has a wide range to help control all biological problems from algae to harmful sludge. Algae is a reality, but there are many things that pond owners can do to create a stable pond environment and reduce the prevalence of outbreaks.

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  • Roselyn Sahlan

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