Hot Weather and Pond Algaecides

Hot Weather and Pond Algaecides

Chris Deer

Summer came in with a BANG this year after such a pleasant mild spring. For some garden pond owners, this has caused algae to bloom in their ponds (especially if you do not use a UV clarifier). When the pond water is cooler (below 80 degrees), the water can maintain strong oxygen levels even in the presence of an algae bloom but once the water warms above 80 degrees, oxygen levels are MUCH lower. For this reason, you must be careful if you use any type of algaecide product in your pond. When an algae killing product is added to a pond with already low oxygen levels, your fish can be killed quickly just by adding an algaecide due to the sudden drop in pH and/or oxygen levels.

This is a major reason customers lose their fish in the summer months in warm climates. The fish seem fine but within an hour of adding an algaecide, the fish rush to the surface suffocating from oxygen depletion. Because of this risk, we do not recommend using an algaecide when the pond water is over 80 degrees!

If you feel the need to use an algaecide in the hot summer months you must first ensure that the oxygen levels in the pond can be sustained before adding the product! If the water is thick with green algae, first perform a large partial water change on the pond using properly conditioned tap water to dilute the amount of free- floating algae in the water.

You should also greatly increase the amount of surface agitation by adding an additional water pump that breaks the surface water or a powerful air pump with an airstone to produce oxygen.

Finally, you must test the pond water to verify that the carbonate hardness (KH) of the water is at least 3 degrees. This will prevent a sudden drop in pH that can also kill your pond fish. Don’t allow your pond fish to be killed by carelessly using an algaecide in hot weather! Of course, there are safer methods than using chemicals to control algae in your garden pond. Good pond maintenance will prevent many algae from growing. Remove dead plant material, dip out tree debris, do monthly 25% partial water changes to dilute the concentration of organics in your pond and use activated carbon in a nylon bag in your pond filter for organic adsorption.

The addition of a UV clarifier will kill all free-floating algae spores in the water giving you crystal clear pond water. These may be more expensive but it will SAFELY kill free- floating algae in your pond.

For algae on the walls of the pond, you can add plecostomus for eating algae. This tropical species will survive all summer long in your pond and you may be able to return the fish to your vendor in late fall once water temperatures dip to 70 degrees. Plecostomus are a fish that have a mouth designed for scraping algae as this is the main diet of these fish. You will be impressed at how much algae will be removed at night by a plecostomus while you are sleeping!

These fish are completely safe with goldfish and koi in a garden pond with algae growth to sustain their diet. Algaecides may seem like a cheap alternative to a UV clarifier but if the product kills your fish from you misusing it, that algaecide can be pretty darn expensive too! Plus, with the amount of money you will spend on water clarifying products in one season can often purchase a UV clarifier for less cost!