Products to Kill Algae

You can cure pond algae problems with chemical or natural products. Algae treatments are most effective when the water temperature is above 50 degrees F. Some algaecides deplete a pond's oxygen content as a side effect of the treatment process, so oxygenate your pond with a fountain or regular manual agitation to maintain healthy oxygen levels. Calculate the volume of your pond in gallons to dose your pond accurately.

  1. Copper Algaecides

    • Chemical-based algaecides containing copper kill pond algae quickly but they are not suitable for some types of garden pond. Copper is toxic to koi fish and pond plants even in low doses and residual copper deposits build up in a pond following treatment, damaging healthy bacteria colonies. Beneficial bacteria keep your pond's ecosystem stable and repeated use of a copper-based algaecide can do more harm than good in the long term.

    Barley Straw

    • Natural algaecides containing barley straw extract or activated barley straw are non-toxic to fish and plants and you can use them in most domestic garden pond setups. Barley straw is safe for use in a koi pond and it works with your pond's healthy bacteria to maintain stable water chemistry during treatment. Liquid or powder forms work equally well and a bundle of raw straw under a pond rock also fixes algae problems.

    Contact Algaecides

    • Contact algaecides do not interfere with a pond's natural bacteria and the active ingredient in most brands is a specially formulated type of peroxide that works on the algae from the outside. This group of algaecides stick to the outer membrane and kill the algae on contact by destroying it at a cellular level. Unlike copper, contact solutions disperse into the water without any residual deposits after treatment.

    Shading Agents

    • Algae flourishes in sunlight and some algae treatments contain a pigment to color pond water, depriving algae of the light it needs to grow. Shading agents block out light by turning the water black or blue, so sunlight is unable to penetrate beneath the water's surface. Shading agents can permanently stain rocks and gravel and some solutions are harmful to fish and plants, so read the manufacturer's recommendations before use.