I’ve found Clathrella species at several locations:

• ditch in Ankeveen, the Netherlands, sporadic, between 1975 and 2000;
• my tropical aquarium (c. 1985);
• dice-shaped specimens in sediment of the Neerbeek-stream in the southern part of the Netherlands (2011);
• large specimens on aquatic plants in a lagoon in the Peruvian rainforest (2012);
• large specimens in two ditches around the Naardermeer, south and north, the Netherlands (2012);
• small specimens in a ditch in the Laegieskamp, the Netherlands (2012);
• many large specimens in a small lake at Lolo Pass, Montana, USA (2013);
• large specimens in a sample from a pond in Wellington, Florida, USA (2014);
• small specimens in a pond near Kootwijk (2014);
• small specimens in a pond near Huizen (2014);
• large specimens in floating sediments, Crailoo (2014-2026);
• small specimens in a small stream in Bretagne, France (2015);
• small specimens near Kornwerderzand, in the IJsselmeer (2015);
• three different species in the Waterleiding Dunes, the Netherlands (2015);
• small specimens in the Heelsumse Beek (2015);
• Lotus pond in China (2015), small and large specimen;
• Glacial stream, El Chalten, Patagonia, Argentina (2017);
• Lake at the Great Alvar, Öland, Sweden (2026).

It seems that this species has a world wide distribution as it is known from Europe and North- and South-America, China and Japan (see the copy of a page of the Japanese website (https://protist.i.hosei.ac.jp) below, where Clathrella erroneously has been identified as Hedriocystis reticulata.) The species has also been found in India (Anagha Datar, pers. comm., 2015)