 Even earlier than the collections in Massachusetts and New York , a population of U. inflata was located in Horseshoe Lake in Kitsap County , Washington in 1980 . Since then , further specimens of U. inflata have been recorded from other Puget Sound area lakes in Kitsap , Mason , Pierce , and Thurston counties . One population has even been recorded from the more southern Silver Lake in Cowlitz County . Information on this species in Washington State provided by the state 's Department of Ecology includes a statement that U. inflata 's presence in Horseshoe Lake was " probably the result of a discarded aquarium . " Washington 's Department of Ecology also indicates that in the areas where it occurs , U. inflata forms dense floating mats , becoming a nuisance for recreational activities . Residents of Lake Limerick , which has extensive populations of U. inflata , spend thousands of dollars each summer to rid their lake of the dense , weedy mats . A variety of control methods have been used to control the weed , including a sonar treatment , biocontrol utilizing grass carp , and manual extraction . Washington considers this species to be problematic but has not classified it as a noxious weed . Instead , it is on a monitor list of wetland and aquatic species under quarantine , meaning that it is prohibited to sell this species and it may be included on the state 's noxious weed list in the future . 
