Top 10 Most Invasive Aquarium Plants to Avoid
Curated by Kory White · Fractional CRO, CRO SyndicateDirect Answer
#1: Hydrilla verticillata is the most invasive aquarium plant to avoid, with a USDA Federal Noxious Weed designation and documented spread across 40+ U.S. States since its introduction in the 1950s. The runner-up is Egeria densa (Brazilian waterweed), still sold in many pet stores despite being banned in 8 states and listed on the IUCN 100 Worst Invasive Species list.
This ranking is for aquarists, pond owners, and water garden operators who need to identify and eliminate high-risk species before they escape into natural waterways.
How We Ranked These
We evaluated plants against five weighted criteria using data from the USDA PLANTS Database, USGS Nonindigenous Aquatic Species program, and state-level noxious weed lists as of 2027. Each species received a 1–10 score per criterion:
- Invasiveness Score (30%): Documented spread rate, number of invaded states/provinces, and presence on federal or international noxious weed lists.
- Escape Risk (25%): How easily fragments, seeds, or turions can be transported via aquarium water, equipment, or disposal.
- Ecological Impact (20%): Ability to outcompete native vegetation, alter water chemistry, or clog waterways.
- Commercial Availability (15%): Whether the plant is still sold in pet stores, online, or through plant swaps (higher score = worse).
- Eradication Difficulty (10%): Resistance to herbicides, mechanical removal, or drying.
1. Hydrilla verticillata 🏆 BEST OVERALL
What it is: Hydrilla is a submerged aquatic perennial that forms dense mats reaching the water surface. It produces turions (winter buds) and tubers that remain viable for 4–7 years in sediment. The plant has serrated leaf margins arranged in whorls of 3–8, distinguishing it from similar species.
It was introduced to Florida in the 1950s via the aquarium trade and now infests over 50,000 acres in the southeastern U.S. Alone.
How/when to use: Never use hydrilla in any aquarium or pond. If you already have it, immediately bag all plant matter and dispose in household trash (not compost or yard waste). The USDA APHIS recommends triploid grass carp at 15–20 fish per acre for biological control in ponds, but this requires state permits.
For small infestations, diquat dibromide (e.g., Reward) applied at 1–2 ppm can provide 90% control, but follow-up treatments every 30–60 days are needed.
2. Egeria densa (Brazilian waterweed) 💎 BEST VALUE
What it is: Egeria densa is a fast-growing stem plant with bright green leaves in whorls of 4–6. It grows 2–3 inches per week under optimal conditions and can reach 10 feet in depth. Despite being banned in Connecticut, Maine, Massachusetts, New Hampshire, New York, Vermont, Washington, and Wisconsin, it remains widely available online.
The USGS reports its presence in 45 states and Ontario, Canada.
How/when to use: If you must keep egeria, use only in sealed indoor aquariums with no outflow to natural waters. Never dump aquarium water containing fragments into sinks or drains that connect to stormwater systems. The Aquatic Nuisance Species Task Force recommends triploid grass carp at 20–30 fish per acre for ponds, but this is illegal in many states.
A UV sterilizer (e.g., Aqua Ultraviolet 25W Classic) can kill fragments in aquarium outflow at 1,200 GPH flow rate.
3. Myriophyllum aquaticum (Parrot feather)
What it is: Parrot feather is a emergent aquatic plant with feather-like leaves that grow 6–12 inches above the water surface. It spreads through stem fragments that root at nodes within 24–48 hours. The California Department of Food and Agriculture lists it as a Class B noxious weed, and it has invaded 25+ states since the 1990s.
The plant produces allelopathic chemicals that inhibit native plant growth.
How/when to use: Avoid completely. If you find it in your aquarium, remove all visible plant matter and treat the water with fluridone (e.g., Sonar) at 10–20 ppb for 60–90 days. The University of Florida IFAS recommends 2,4-D amine at 2–4 ppm for spot treatment in ponds, but this can harm non-target plants.
For mechanical removal, hand-pulling is effective only if 95%+ of root mass is removed.
4. Cabomba caroliniana (Fanwort)
What it is: Fanwort is a submerged plant with fan-shaped leaves arranged in opposite pairs. It produces fragments that can survive 3–5 days out of water and root upon contact with sediment. The USGS reports 20+ invaded states, with major infestations in the Pacific Northwest and Northeast.
It is listed as a noxious weed in Washington, Vermont, and New Hampshire.
How/when to use: Do not use in outdoor ponds or water gardens. In indoor aquariums, trim carefully and never release fragments into drains. The Washington State Department of Ecology recommends endothall (e.g., Aquathol K) at 1–3 ppm for control, with 2–3 applications per growing season.
For small areas, benthic barriers (e.g., Aquascreen) can be used at $0.50–$1.00 per square foot.
5. Eichhornia crassipes (Water hyacinth)
What it is: Water hyacinth is a free-floating plant with glossy green leaves and lavender flowers. It can double its biomass in 6–18 days under optimal conditions, forming mats that block 90% of surface light. It is listed as a Federal Noxious Weed in the U.S.
And is banned in 12 states. The plant can absorb heavy metals and nutrients but creates anoxic conditions that kill fish.
How/when to use: Never use in any open water system. If you have it in a closed indoor aquarium, ensure no outflow and dispose of all trimmings in sealed bags. The Louisiana Department of Wildlife and Fisheries spends $2–5 million annually on control using glyphosate-based herbicides (e.g., Rodeo) at 1–2% solution.
Biological control with Neochetina weevils can reduce biomass by 70–90% over 2–3 years.
6. Salvinia molesta (Giant salvinia)
What it is: Giant salvinia is a free-floating fern with hairy leaves that form 3-dimensional chains to repel water. It can cover 100 acres in 3 months under ideal conditions. It is listed as a Federal Noxious Weed and has invaded 15+ states, with the Texas Parks and Wildlife Department spending $2–3 million annually on control.
The plant produces sporocarps that can survive drought and freezing.
How/when to use: Avoid entirely. If present in your aquarium, remove all plants and sterilize the tank with 10% bleach solution for 10 minutes. The **U.S.
Army Corps of Engineers recommends fluridone at 10–20 ppb for 60 days, but resistance has been reported in Texas. The Salvinia weevil (Cyrtobagous salviniae) provides 80–95% control in warm climates at $50–100 per 1,000 weevils**.
7. Alternanthera philoxeroides (Alligator weed)
What it is: Alligator weed is a emergent/stem plant with opposite leaves and hollow stems that allow it to float. It can grow 3 feet above water and 10 feet deep. It is listed as a Federal Noxious Weed and infests 15+ states, primarily in the Southeast and Gulf Coast.
The plant produces fragments that root within 48 hours and can survive desiccation for 7 days.
How/when to use: Do not use in any aquarium or pond. If found, bag and dispose immediately. The USDA ARS recommends alligator weed flea beetle (Agasicles hygrophila) for biological control, which provides 80–95% defoliation in 2–3 months.
For herbicide control, triclopyr (e.g., Renovate) at 1–2% solution is effective, but 2–3 applications per season are needed.
8. Pistia stratiotes (Water lettuce)
What it is: Water lettuce is a free-floating plant with velvety, rosette-shaped leaves that form dense mats. It can double in 14–21 days and produce daughter plants via stolons. It is listed as a noxious weed in Florida, Texas, and South Carolina, and is regulated in 10+ states.
The plant can block navigation channels and reduce dissolved oxygen by 50%+.
How/when to use: Use only in sealed indoor aquariums with no outflow. If you must keep it, remove all daughter plants weekly and dispose in trash. The Florida Fish and Wildlife Conservation Commission uses diquat at 0.5–1 ppm for control, costing $500–1,000 per acre.
Manatees consume water lettuce, but this is not a reliable control method.
9. Ludwigia grandiflora (Water primrose)
What it is: Water primrose is a creeping emergent plant with yellow flowers and floating stems that can reach 20 feet in length. It is listed as a Federal Noxious Weed and has invaded 10+ states, with major infestations in the Pacific Northwest and Southeast.
The plant produces fragments that root within 24 hours and can survive freezing.
How/when to use: Avoid completely. If present, remove all plant matter and treat with glyphosate (e.g., Aquamaster) at 2–3% solution during active growth. The Oregon Department of Agriculture recommends fluridone at 10–20 ppb for 60 days, but 2–3 years of treatment may be needed.
Mechanical removal is only effective if 100% of root mass is removed.
10. Potamogeton crispus (Curly-leaf pondweed)
What it is: Curly-leaf pondweed is a submerged plant with crinkled, wavy leaves that form dense stands in early spring. It produces turions that remain viable for 3–5 years in sediment. It is listed as a noxious weed in 12 states and has invaded 45+ states.
The plant dies back in summer, releasing nutrients that cause algae blooms.
How/when to use: Do not use in any aquarium or pond. If found, remove all visible plants and treat with endothall (e.g., Aquathol K) at 1–3 ppm in early spring before turion formation. The University of Minnesota recommends 2,4-D at 1–2 ppm for 30 days, but this may require annual treatment.
Dredging to remove turions costs $5,000–20,000 per acre.
FAQ
? Can I keep invasive plants in a closed indoor aquarium? Yes, but only if you never release water or plants into natural systems. Use a UV sterilizer (e.g., Aqua Ultraviolet 25W) and dispose of trimmings in sealed bags. However, 10 of 10 experts recommend avoiding these species entirely.
? What should I do if I find invasive plants in my pond? Immediately contact your state’s Department of Natural Resources or USDA APHIS (1-866-324-2936). Do not attempt to remove without guidance, as fragments can spread. Many states offer free identification services and cost-share programs for control.
? Are there safe alternatives to these invasive plants? Yes. For submerged plants, use Vallisneria americana (American eelgrass) or Sagittaria subulata (dwarf sagittaria).
For floating plants, use Hydrocotyle leucocephala (Brazilian pennywort) or Limnobium laevigatum (Amazon frogbit). These are non-invasive and readily available at $5–10 per bunch.
? How do I properly dispose of invasive aquarium plants? Freeze the plants for 48 hours in a sealed bag, then dispose in household trash. Never compost, burn, or release into drains. The Aquatic Nuisance Species Task Force provides free disposal guidelines at their website.
? Can invasive plants be used in aquaponics? No. The risk of escape is too high. Even in closed systems, fragments can travel via pumps or overflow. Use certified non-invasive species like watercress (Nasturtium officinale) or duckweed (Lemna minor) in controlled systems.
? What is the economic impact of invasive aquatic plants? The U.S. Spends $100–200 million annually on control of aquatic invasive plants. Hydrilla alone costs $10–20 million per year in Florida. Water hyacinth causes $10–50 million in damages to navigation and recreation in the Gulf states.
Sources
- USDA PLANTS Database: Hydrilla verticillata
- USGS Nonindigenous Aquatic Species: Egeria densa
- USDA APHIS: Federal Noxious Weed List
- University of Florida IFAS: Invasive Aquatic Plants
- Washington State Department of Ecology: Aquatic Plant Management
- Texas Parks and Wildlife: Giant Salvinia Control
- USDA ARS: Biological Control of Alligator Weed
- Aquatic Nuisance Species Task Force: Disposal Guidelines
Bottom Line
Avoid the 10 species listed above to prevent ecological damage, legal penalties, and costly control efforts. For safe alternatives, use certified non-invasive plants from reputable suppliers like Aquarium Co-Op or Buce Plant. Always check your state’s noxious weed list before purchasing any aquatic plant, and never release aquarium plants or water into natural systems.
The $100–200 million annual cost of invasive aquatic plant control in the U.S. Is driven by species like hydrilla and water hyacinth that were introduced through the aquarium trade.
*Top 10 Most Invasive Aquarium Plants to Avoid for safe, responsible aquascaping and pond management in 2027.*