Grass Carp

If your pond has a weed or algae problem, it can be a terrible nuisance. Many pond owners are reluctant to pour chemicals into their ponds, and for good reason. Fortunately, there are biological, environmentally responsible ways to control aquatic vegetation, including proper aeration systems and the introduction of triploid grass carp into the lake or pond.

Grass Carp in combination with aeration is the best “multi-parameter” biological / mechanical approach to managing the weed and algae population in a pond. Rowledge Pond Aquaculture can help you with many aspects of aquatic plant management, including supplying grass carp, meeting DEEP requirements, and suggesting aeration systems. Read on to learn more about Grass Carp and the DEEP permitting process, or contact us to begin the journey toward a healthier pond or lake.

Triploid Grass Carp FAQ’s

Grass Carp for Pond HealthWhat do they look like? Triploid Grass Carp are not ornamental carp. They are all drab silver in color and have large scales. They have an elongated body shape, and can become quite large. Carp reaching lengths of 24-36” after a few years are not uncommon.

How do I stock Grass Carp in my pond? Rowledge Pond is a certified supplier of Triploid Grass Carp for the states of Connecticut and New York. All fish are delivered–the hatchery does not allow the pick-up of fish by the public. The delivery charges are based on the distance of the targeted pond from the hatchery. Each stocking of grass carp is quoted on an individual basis, but the cost per fish is $18. All fish are certified by US Fish & Wildlife Service. Every stocking requires a state permit. Please obtain a permit first, then contact us to get a quote and set up delivery.

Does my lake need a permit to stock grass carp? Yes, a liberation permit is required to stock Grass Carp. Please see our Permit Page for more information.

How effective are Grass Carp? Grass Carp can be extremely effective at controlling excess weed and algae growth. Their effectiveness is somewhat dependent on both the type of aquatic weeds as well as the density. In general Grass Carp are effective at controlling most submerged or floating vegetation. Grass Carp will neither control planktonic algae (microscopic) nor will they control emergent vegetation like cattails. The CT DEEP Inland Fisheries Division can assist you in determining the type and density of weeds in your pond or lake.

How cost-effective are Grass Carp compared with other vegetation control methods? Grass Carp are perhaps the most cost-effective approach, depending on weed type. In general there are four methods for removing and/or controlling aquatic vegetation. They include; biological control with Grass Carp, the application of chemical herbicides, mechanical harvesting, and depth management through bottom dredging. Mechanical harvesting and dredging can be extremely costly (tens of thousands of dollars each time). Chemical herbicides are costly and most often need to be reapplied every year, if not a couple of times a year. Grass Carp have a relatively low initial cost and typically are only restocked every 5-6 years.

Do Grass Carp eat other fish? No, Grass Carp do not eat other types of fish, they only eat vegetation. However, there can be an indirect effect on the resident fish population, as a result of the consumption of vegetation by the grass carp. Aquatic vegetation provides cover for juvenile fish and forage fish, as well as a spawning substrate for some fish species. Therefore, the objective for the grass carp stocking should not be to eradicate the aquatic vegetation in the pond or lake, but rather to control the growth and extent of aquatic vegetation.

Will the Grass Carp survive through the winter? Yes, provided that your pond or lake is at least four feet deep. You need to have adequate depth in the pond to ensure sufficient water volume under the ice. Grass Carp, like other indigenous (native) fish, can be lost if the pond experiences a winter-kill. A winter-kill typically occurs when the oxygen level in the water drops so low that the fish can no longer survive. Contact Rowledge Pond Aquaculture or the CT DEEP Inland Fisheries Division to lean more about winter-kill.

Do I need to restock every year? Typically Grass Carp will live 5-6 years. Thus you no not need to restock every year, but rather every five or six years, if needed. Often your second stocking will be smaller than the initial stocking.

Will they reproduce? No, Triploid Grass Carp are sterile. Subsequently, the fish grow larger and faster because they are not spending any energy on reproduction.

Do they have any predators? Yes, great blue herons and otters are the most common predators. Very large bass and large snapping turtles can also prey on Grass Carp.

Do they “muddy-up” the pond? No, unlike common carp, Grass Carp do not feed on the bottom of the pond and thus do not increase the water turbidity or “muddy-up” the pond. Grass Carp feed throughout the water column as well at the water surface.

How many should I stock? The number of Grass Carp you stock is dependent on weed type, weed density, the size of the pond or lake, and most importantly, your pond or lake management objectives. Any state fisheries biologist can assist you in determining the appropriate number of carp to stock at the time of the pond or lake inspection to obtain approval for liberation. To learn more, visit the CT DEEP Grass Carp web page or download the Grass Carp Manual.

Can I use herbicides in my pond if I have Grass Carp? It is not recommended that you use herbicides and Grass Carp simultaneously. Grass Carp are extremely sensitive to many aquatic herbicides, particularly those containing copper. Treating a pond or lake with herbicides may eliminate the food source for the Grass Carp, and will most likely be overkill. There are certain circumstances when both Grass Carp and herbicide application may be appropriate to achieve your weed management objectives. Consult Rowledge Pond Aquaculture or the CT DEEP Inland Fisheries Division for more details. Be advised that an aquatic herbicide permit is required. Contact the DEEP Pesticide Management Program for more information.

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DEEP Permit Process

A liberation permit is required to stock Grass Carp. There is no cost for the permit, and the permit process is relatively easy, especially if your pond is smaller than 20 acres. (Larger lakes may require more extensive analysis.) Connecticut residents can contact the CT DEEP Inland Fisheries Division for more information and download the permit application. Be advised that Triploid Grass Carp can only be liberated after the DEEP Fisheries Division has inspected your pond or lake and has determined that a permit can be issued. New York residents, please visit the New York Department of Environmental Conservation website for more information on New York’s grass carp policies.

Emigration Control Screens Frequently, the DEEP Fisheries Division inspection will determine that a pond or lake requires a Grass Carp Emigration Control Screen before grass carp can be liberated.

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