Grass carp
Ctenopharyngodon idella
Water parameters
Minimum tank: 2000 L per individual at harvest size.
Feed and growth
- Feed protein
- 25% target
- Daily feed (warm)
- 3.00% of body weight
- Daily feed (cool)
- 0.80% of body weight
- Max density
- 35 g per litre
A 15000 g adult eats about 450.0 g of feed per day at optimum. 10 fish at adult size: ~4500 g daily.
Legality
Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.
| Jurisdiction | Status | Notes |
|---|---|---|
| United States (federal) | triploid (sterile) form only | Diploid (fertile) grass carp prohibited or strictly regulated in most US states; triploid sterile form permitted for vegetation control in many states verified 2026-05-13 |
| California | prohibited | California prohibits both diploid and triploid grass carp verified 2026-05-13 |
| Washington | prohibited | verified 2026-05-13 |
| Oregon | prohibited | verified 2026-05-13 |
| New South Wales | prohibited | verified 2026-05-13 |
| Queensland | prohibited | verified 2026-05-13 |
| European Union (bloc) | check local regulations | Permitted in some Eastern European aquaculture; restricted elsewhere verified 2026-05-13 |
Unlisted jurisdictions default to "check local regulations".
Origin and habitat
Native to large rivers in eastern Asia, from the Amur River (Russia-China border) south through China to Vietnam. The species (Ctenopharyngodon idella) is a herbivorous carp that feeds exclusively on aquatic and terrestrial vegetation. Adults are large: 1–1.5 m and up to 45 kg, though culture harvest size is typically 1–5 kg. Grass carp are one of the four traditional Chinese culture carps (along with bighead carp, silver carp, and black carp) and are produced in enormous quantities: over 5 million tonnes annually, making them the most produced freshwater fish species in the world. The species has been introduced to over 80 countries for aquatic weed control and aquaculture, and has become invasive in several waterways, particularly in the Mississippi basin where naturalized populations now reproduce.
Climate and outdoor ponds
- Climate
- temperate (handles seasonal swings)
- USDA zones
- 3–12 (winter low around -40°C or warmer)
- Heating needed
- no
- Cooling needed
- no
Care notes
A herbivorous fish that can reduce feed costs in aquaponics by consuming plant waste (duckweed, vegetable trimmings, grass clippings, aquatic weeds) directly. This makes grass carp uniquely efficient in integrated systems where plant biomass is abundant. Temperature range: 10–33°C, optimal at 25–30°C. Growth on vegetation alone is 1–3 kg in 12-18 months in warm conditions. Supplemental commercial pellet (25-30% protein) accelerates growth; FCR on pellet is 1.5-2.5, but the real efficiency is in the ability to convert low-value plant waste into fish protein. Stocking density: 10-20 g/L. Grass carp are heavily regulated in many jurisdictions because of their invasive potential. In many US states, only triploid (sterile) grass carp are legal, and a permit is required. Australia prohibits grass carp entirely. Some European countries allow culture under controlled conditions. Check local regulations before acquiring stock. Triploid fingerlings are available from certified hatcheries in the US. The flesh is white and acceptable but bony; market acceptance varies. For aquaponics, grass carp are most valuable as plant-waste recyclers in polyculture with another species (like tilapia) rather than as the primary harvest fish.