St. Louis Water Gardens: How to Defeat The Green Monster!

Green Algae:  The  ‘Green Monster’ of  Your Water Garden

It’s the scourge of backyard water gardeners everywhere.  Variously called "green water," "blanket weed" or “pond scum,” it’s known to scientists as thallophytes and to less-emotional water gardeners as green algae. 

Algae live just about anywhere you have light and water:  in puddles, soil, even in your bathroom shower. It should come as no surprise that algae can grow like crazy in water gardens.  Algae spores can enter your pond by wind, rain, on the sides of fish and on water plants you introduce into the pond. Single-celled green algae may form "pea soup" blooms, taking over your pond and overwhelming fish and submerged plants.  

Can algae be defeated by backyard gardeners?  No – and it shouldn’t be, at least not completely.  That’s because algae is an essential part of the natural food chain in all water gardens.  Algae keeps the pond "in balance," helping to maintain a healthy environment for fish and other pond creatures.  But there’s another reason why you shouldn’t try to eradicate green algae completely – it’s impossible.

Why? Because, compared to nature, backyard water gardens contain several thousand times the number of fish and plants per gallon of water.  Although we like to think that water gardens mimic nature, man-made ponds are very unnatural in just about every biological and chemical aspect.

So what’s a backyard water gardener to do when it comes to staring down algae?

1. Don’t put too many fish in the pond. More fish means more waste released into the water. As fish waste breaks down, it releases nutrients like phosphates and nitrates for algae to feast upon.
2. Introduce lots of aquatic plants. Aquatic plants reduce algae growth by removing excess nutrients from the water.  Try to cover 50% of pond surface with floating plants like water lilies and water hyacinths and submerged plants like Cabomba.
3. Snails and tadpoles eat “pond scum” algae. Add a few Japanese trapdoor snails and tadpoles.

Sometimes all efforts of "natural" methods don't seem to work, or you've run out of time and patience. In that case, an algaecide like PondCare AlgaeFix® can be your answer. Biological filtration can also help; it’s designed to remove harmful ammonia released by fish, decomposing plants and algae, and uneaten fish food.

The best way to control algae problems naturally is to minimize the amount of phosphate and nitrate in the water.  You can limit these nutrients by limiting the number of fish, limiting  the amount you feed them, and adding plenty of aquatic plants to the pond.