Green water is a problem that lots of pond and aquarium owners suffer from – there is a simple reason behind it! Fish! When we keep fish in our ponds and tanks, they inevitably produce waste, which drops to the bottom of the tank or pond. This waste is eaten up by bacteria in the water, which is a good thing, otherwise the water would become overridden with waste product… The bacteria turn the waste into nitrates, which is the perfect food for algae and plants. As the algae eats up the nitrates, it grows larger, and sunlight helps it to grow too. This is why ponds often look greener during the summer months, when it is warmer and sunnier most days.
There are ways to get rid of excess algae – the first is to use chemicals known as algaecides. These kill off the algae, but will not get rid of the problem altogether. To reduce the amount of algae that grows, you will need to keep your pond free from excess fish waste, by removing it manually. You can use a net with a long handle in a pond to sweep the sludge from the bottom of the pond. By getting rid of the waste, you effectively get rid of the algae’s food supply, hence starving it.