Alligator weed (Alternanthera philoxeroides) care guide

Group
Plants
Other names
Achyranthes philoxeroides
Family
Amaranthaceae (amaranth family)
Origin
Temperate South America (Paraná basin: Argentina, Brazil, Paraguay, Uruguay)
Water
freshwater
Maximum size
1000 cm
Care level
beginner
Lighting
Full sun; grows in or out of water

Care

Legal note: this plant may not be sold on Aquatic-Auctions to buyers in Great Britain. It is on the GB list of invasive species (check GOV.UK for the current rules). Alligator weed (family Amaranthaceae) comes from temperate South America, originally the Paraná river region of Argentina, Brazil, Paraguay and Uruguay. It grows both on land and in water, with hollow, sprawling stems that float and runners that can reach 10 m, and small white papery flowers in dense heads. It has spread to more than 30 countries and is one of the world's worst wetland weeds. Its mats shade out native plants, block water flow and oxygen exchange, raise flood risk and breed mosquitoes. It spreads almost entirely from fragments: a tiny piece of stem can start a new colony, and careless removal makes things worse. It has been on the EU list of invasive species of Union concern since 2017, banning import and trade in the EU. There is no good reason to keep it in an aquarium; red Alternanthera reineckii is the aquarium plant usually wanted. If you find it, bag it and dispose of it as household waste, never in compost, drains or waterways. Never release this plant or dispose of it in drains or waterways; it is invasive in some countries. Sources: Wikipedia (en.wikipedia.org/wiki/Alternantheraphiloxeroides); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.

Breeding

Spreads from stem and leaf fragments; rarely sets viable seed outside its native range. Do not propagate.

Compatibility and tank mates

Not for aquariums or ponds. Banned from sale to buyers in Great Britain and throughout the EU.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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