The Asellus was found in slow flowing leaf litter, and the Gammarus prefered more open water where there were rocks, pebbles and riffles.
Nearly all the culture methods use paper towels or cardboard. It is the standard culture method used for ecotoxicology studies.This is what i looked at:https://www.eeob.iastate.edu/faculty/DrewesC/htdocs/LVCULT.htm