What Kind of Carp Keeps Down Algae?

Given the right conditions, algae can multiply rapidly and choke out the ecosystem of many lakes and ponds. Many communities have chosen to deal with out-of-control algae populations by using the natural solution of bringing in carp, many of which feed mostly on grass and algae. While these fish can be a viable solution to a major problem, using carp to keep down algae comes with some serious and legitimate concerns.

  1. Grass Carp

    • Any type of grass carp feeds on a majority of weeds and algae. In the United States, most fish referred to as grass carp are white amur, which can help control the algae population in a pond or lake. These extremely resilient carp feed mostly on plant matter; in a small body of water such as a farm pond, it only takes a few to really clean up the area. In fact, grass carp can eat up to three times their body weight in algae per day.

    Bream

    • Though a European fish in the carp family, the bream often has more of an association with sunfish than with other carp. However, these fish grow at a much slower rate than grass carp and tend to max out at around 13 lbs., making them much easier to contain. Bream are not as popular an option as grass carp for controlling algae, but they are a viable option from the carp family.

    Legal Requirements

    • Many states have strict rules when it comes to using grass carp to control algae. Grass carp breed more frequently than many other freshwater fish and can grow to large enough sizes where they squeeze out the food supply of native fish native populations. For example, in Washington state, the fish must come from fish farms and be sterile so they can't breed and infect the surrounding waters.

    Invasive Species Concerns

    • The largest concern with using carp to cut down on local algae center of their status as an invasive species in the United States that have often squeezed out native game fish far more popular with local anglers, such as walleye, bass, bluegill or trout. As such, carp must generally be sterile and kept in smaller contained environments such as ponds or small self-contained lakes.