Grass Carp Stocking

Triploid grass carp have been legal in South Carolina since 1983 for the biological control of aquatic weed species in ponds and lagoons. Normal recommended grass carp stocking rates will range from 5-20 fish/surface acre. Stocking rate is dependent on the amount of aquatic plant biomass in your pond.

My comments and recommendations for the use of these fish for aquatic weed control are as follows:


  1. Before considering these fish for aquatic weed control in your pond, you should have the nuisance aquatic weed species properly identified. There are some aquatic weed species that the fish will not control! Grass carp are not planktonic or filamentous algae eaters! Grass carp prefer submerged aquatic weed species that have soft stems and leaves.
  2. If your pond has multiple noxious aquatic weed species, grass carp will choose the plant species they prefer to eat and concentrate solely on that plants species until all of it is consumed, then the fish will move on to the next desirable aquatic weed species.
  3. If your pond has potential grass carp predators (largemouth bass, osprey, blue herons, or otters. You should use the largest grass carp available from your grass carp vendor. The largest fish provided by grass carp producers for commercial sale normally is a 12 inch or larger fish.
  4. Normal recommended grass carp stocking rates will range from 5-20 fish/surface acre. Stocking rate is dependent on the amount of aquatic plant biomass in your pond. If your pond has a major aquatic weed infestation, you should use the 20 fish/surface acre stocking rate. If you have a 10 acre pond, but aquatic weeds are only infesting 5 acres of the pond, stock only 100 fish. Grass carp are a non-indigenous fish species and a SCDNR permit for possession is required at time of purchase. Permits can be obtained from the SCDNR or from a permitted Commercial Aqua culturist. I can provide this permit for you!
  5. After stocking your grass carp, under most circumstances it will take the fish 6-12 months to provide the desired control on your aquatic plant pests.
  6. There are three major reasons grass carp do not provide the desired aquatic weed control: (1) Fish do not eat the aquatic weed species present in the pond, (2) Improper stocking rates, and (3) Excessive predation on the grass carp. Grass carp can be caught on earthworm, crickets, or dough-balls. Fishermen who use your pond should be made aware that you have stocked the fish and if caught should be released immediately back into the pond.
  7. Assuming that the correct number and size of fish are stocked, grass carp normally provide five to ten years of biological weed control. If over time you do not see your stocked grass carp in your pond, or if you observe the regrowth of submergent noxious aquatic weeds in your pond, it is then time to restock grass carp. Grass carp mortality studies of fish stocked in large reservoirs have show an annual mortality rate of 18% to 22% with the highest mortality rates on age 1 fish. Assuming a variation of mortalities similar to this study, losses due to mortality of 100 stocked age one grass carp over a five year period would be approximately 66 fish.
  8. Grass carp are not bottom feeders and do not muddy the pond water. They do not bother other fish species spawning areas. They do consume insects and other invertebrates, and directly compete with other fish species for food items. If the sole purpose for having your pond is to provide a managed sport-fishing population, I do not recommend grass carp for aquatic weed control.
  9. I provide only 12 inch or larger grass carp! Cost for these fish are $11.00 - $12.00 per fish. Cost is dependent on the number of fish ordered. I guarantee my fish for 72 hrs. post-stocking. If there are mortalities within this time period that are over 5% of the fish stocking total, I will replace those fish at no charge to the customer. If mortalities occur, pond owner must document the mortalities (photo of all dead fish taken with all fish shown in the one photo). I must be notified via phone call at the time of the mortalities and within the 72 hr. time period post-stocking. Guarantee is not valid if other fish species mortalities occur at the same time as the grass carp mortalities.


If you have any questions or require further information from me on triploid grass carp or pond management, please give A.M.S a call.