For mechanical filtration of coarse and fine dirt particles.
 
Sera filter wool, also known as filter floss, is used for mechanical filtration consisting of stable fibers that retain finer dirt particles for a longer time without sticking or collapsing. Sera filter wool can be washed out several times. Suitable for all filters. Comes in coarse (coarser/larger particles) and fine (dinner particles/polisher).
 
We use this to help polish the water after maintanance or when setting up a new aquarium. 
 
Rinse in warm water before use.