Invasive aquarium plants and how to dispose of trimmings safely

Published October 15, 2026Not yet reviewed by the editor15 sources

Short answer

Several aquarium plants now grow wild in the United States; the USGS records Hygrophila polysperma, Rotala rotundifolia, Cabomba caroliniana and Egeria densa among them [3, 4, 5, 6]. Hygrophila polysperma and Limnophila sessiliflora are federal noxious weeds that may not be moved into or through the US or between states without a permit [1, 2]. Never release plants or tank contents into the wild; the Habitattitude program advises bagging unwanted plants and putting them in the trash [10].

Aquarium plants in the wild

The traits that make a good aquarium plant, fast growth and easy propagation from cuttings, can also help a plant spread once it escapes; several of the records below describe spread from fragments. The US Geological Survey’s Nonindigenous Aquatic Species database documents several familiar aquarium species growing wild in the United States:

Plant How it got out, per USGS Status, per USGS
Hygrophila polysperma Introduced into Florida via the aquarium industry in the 1950s Established in Alabama, Florida, Kentucky, Mississippi, South Carolina and Texas; forms dense stands that exclude native plants [3]
Rotala rotundifolia Popular in the water-garden trade Established in south Florida; spreads from stem fragments that root at the nodes, and from seed [4]
Cabomba caroliniana A 1935 release from an aquarium in the Lake Michigan drainage Established and widely distributed; brittle stems break apart and spread [5]
Egeria densa Introduced worldwide through the aquarium trade, sold as an “oxygenator” Established in many US river basins [6]
Cryptocoryne wendtii Likely escaped from cultivation Recorded in Florida (1989–2001); status and impacts unknown [7]

Two details stand out. Cabomba caroliniana is native to parts of the southern and eastern United States as well as South America [5], so “non-native” depends on where you live. And the USGS explains the crypt records by chemistry: crypts can establish in Florida’s karstic springs, likely because they can use bicarbonate, which those waters supply [7]. Tropica notes that Sri Lankan crypts such as C. wendtii grow well in hard water [8]; our reading (an inference) is that the same tolerance that makes them easy in the aquarium lets them survive in those springs.

Federal noxious weeds

The US federal noxious weed list, 7 CFR 360.200, includes a section of aquatic and wetland weeds. Two of the plants profiled on this site are on it: Hygrophila polysperma (Miramar weed) and Limnophila sessiliflora (ambulia). The same section lists, among others, Hydrilla verticillata, Lagarosiphon major, Ottelia alismoides and four species of giant salvinia [1]. Under 7 CFR 360.300, no person may move a federal noxious weed into or through the United States, or between states, without an approved permit [2].

States keep their own lists of noxious plants and nuisance aquatic species [10]. One plant profiled on this site is an example: Amazon frogbit (Limnobium laevigatum). California lists it as a noxious weed with an “A” pest rating, so it may not be brought into the state without a CDFA or USDA permit for contained exhibit or research [13, 14]; Washington lists it as a Class A noxious weed and on its quarantine list, which prohibits transporting, buying, selling or distributing it into or within the state [15]. We do not summarize other state lists here; check your state’s agriculture or natural-resources agency.

Outside the United States the rules differ. The European Union keeps a list of invasive alien species of Union concern, last updated by a regulation that entered into force on 7 August 2025 [11]. We have not reproduced its species list; check the current consolidated version before buying or trading plants in the EU.

Hitchhikers

Plants can carry other organisms. In March 2021 zebra mussels, an invasive freshwater mussel, were found attached to imported marimo balls in some pet stores in 29 US states [9]; our marimo profile has the details. The Habitattitude program advises checking roots and soil for unwanted visitors before planting [10]. Tissue-culture plants avoid most of this: Aquasabi notes that in-vitro plants are free of snails, planarians, insect larvae, algae and weeds such as duckweed [12].

Disposing of trimmings and unwanted plants

  1. Never release plants or tank contents into ponds, streams or drains. Several of the species above spread from fragments [4, 5].
  2. Bag and bin. Habitattitude’s advice for unwanted aquatic plants is to put them in plastic bags and discard them in the trash [10].
  3. Buy by scientific name. Habitattitude recommends buying from sources that state the scientific name, so you can check it against your state’s lists [10]. Our plant profiles give the accepted name from the World Checklist of Vascular Plants for that reason.
  4. Choose natives or non-invasive species for outdoor use. For water gardens, Habitattitude recommends species native to your area or not considered invasive, and ponds built so they cannot overflow into public waters [10].

This page summarizes official sources on the dates shown and is not legal advice; see our disclaimer.

Questions

Can I compost aquarium trimmings?

The official advice we found does not cover composting; the Habitattitude program's advice is to put unwanted plants in plastic bags and in the trash [10]. Because many of these plants regrow from small fragments [4, 5], bagging is the safer default.

Is it legal to keep Hygrophila polysperma in the United States?

Federal rules restrict moving it into or through the United States and between states without a permit [2], and states may have their own lists [10]. This page is not legal advice; check with your state agriculture or natural-resources agency.

Are tissue-culture plants safer?

They avoid hitchhikers: Aquasabi notes that in-vitro plants are free of snails, algae and unwanted plants such as duckweed [12]. They do nothing about the plant itself becoming invasive.

Plants mentioned

Related guides

Sources

  1. 7 CFR 360.200, Designation of noxious weeds. Electronic Code of Federal Regulations (eCFR), U.S. Government. Aquatic and wetland weeds include Azolla pinnata, Hydrilla verticillata, Hygrophila polysperma, Lagarosiphon major, Limnophila sessiliflora, Ottelia alismoides, Sagittaria sagittifolia and four giant Salvinia species (text as of 2026-10-08). Accessed October 12, 2026.
  2. 7 CFR 360.300, Notice of restrictions on movement of noxious weeds. Electronic Code of Federal Regulations (eCFR), U.S. Government. No person may move a Federal noxious weed into or through the United States, or interstate, unless under an approved permit. Accessed October 12, 2026.
  3. Hygrophila polysperma: fact sheet. U.S. Geological Survey, Nonindigenous Aquatic Species database. Introduced into Florida via the aquarium industry in the 1950s; established in AL, FL, KY, MS, SC and TX; forms dense monocultures that exclude native plants. Accessed October 12, 2026.
  4. Rotala rotundifolia: fact sheet. U.S. Geological Survey, Nonindigenous Aquatic Species database. Popular in the water-garden trade; established in south Florida; spreads from stem fragments that root at the nodes and from seed; can form dense submersed stands. Accessed October 12, 2026.
  5. Cabomba caroliniana: fact sheet. U.S. Geological Survey, Nonindigenous Aquatic Species database. Native to southern South America and the southern and eastern USA; 1935 release from an aquarium in the Lake Michigan drainage; brittle stems fragment and spread vegetatively; established in many states. Accessed October 12, 2026.
  6. Egeria densa: fact sheet. U.S. Geological Survey, Nonindigenous Aquatic Species database. Introduced worldwide through the aquarium trade, sold as an 'oxygenator'; established in many US basins; dense stands restrict water movement and recreation. Accessed October 12, 2026.
  7. Cryptocoryne wendtii: fact sheet. U.S. Geological Survey, Nonindigenous Aquatic Species database. Popular aquarium plant that likely escaped from cultivation in Florida; crypts establish in karstic spring-fed waters, likely because they can use bicarbonate; impacts unknown. Accessed October 12, 2026.
  8. Cryptocoryne wendtii 'Green' (plant details, 109). Tropica Aquarium Plants. Like most other Sri Lanka Cryptocorynes, it also grows well in hard water. Accessed October 12, 2026.
  9. Zebra mussel (Dreissena polymorpha): species profile. U.S. Geological Survey, Nonindigenous Aquatic Species database. March 2021: zebra mussels found on imported Marimo balls in pet stores of 29 states. Accessed October 12, 2026.
  10. Water gardening. Habitattitude (sponsored by Pet Advocacy Network, U.S. Fish and Wildlife Service and NOAA). Choose native or non-invasive species; many plants regulated as noxious or nuisance species; buy with scientific names; check roots and soil for hitchhikers; dispose of plants in plastic bags in the trash. Accessed October 12, 2026.
  11. Invasive alien species. European Commission, Directorate-General for Environment. List of invasive alien species of Union concern; fourth update entered into force on 7 August 2025 (Implementing Regulation (EU) 2025/1422). Accessed October 12, 2026.
  12. Tissue-culture or potted plants?. Aquasabi (aquascaping wiki). In-vitro plants are free of pesticides, parasites, snails, planarians, insect larvae, algae and weeds such as duckweed. Accessed October 12, 2026.
  13. CDFA Weed Pest Ratings and CCR 4500 Noxious Weeds (as of June 22, 2021). California Department of Food and Agriculture. Limnobium laevigatum, South American spongeplant: CDFA pest rating A, and on the California Code of Regulations section 4500 noxious weed list. Accessed October 14, 2026.
  14. Noxious weed ratings: definitions. California Department of Food and Agriculture. A-rated pests are prohibited from entering the state except with a CDFA or USDA permit for contained exhibit or research; if found, they are subject to state-enforced eradication, quarantine, containment, rejection or other holding action. Accessed October 14, 2026.
  15. South American spongeplant (Limnobium laevigatum). Washington State Noxious Weed Control Board. Class A noxious weed, listed 2020; on the Washington State quarantine list (WAC 16-752), which prohibits transporting, buying, selling, offering for sale or distributing plants or plant parts into or within Washington. The listings also appear in WAC 16-750-005 and WAC 16-752-610 (read in archive.org copies of May 2026; the legislature's site did not answer scripted requests). Accessed October 14, 2026.