Crassula helmsii, also known as Australian swamp stonecrop or New Zealand pygmyweed, is a perennial swamp and water-based plant that originated in Australia and New Zealand and is not native to the Netherlands. The plant is sold for use in aquariums and ponds. Wild Crassula helmsii was first observed in the Netherlands in 1995. Since then, it has been observed in more locations (NDFF, 2020), including in nature conservation areas. The plant competes with other plants. Eradication measures have been largely ineffective and so far have only successfully eliminated small infestations in isolated bodies of water (Van der Loop et al., 2018). The plant is considered an invasive species in a variety of European countries (Robert et al., 2013). As a result of these developments, the Office for Risk Assessment & Research (BuRO) at the Netherlands Food and Consumer Product Safety Authority (NVWA) initiated a study to examine the risks posed by Crassula helmsii