It depends on the speed of filtering that you require, but I always use an aquarium "bubbler" stone, attached to a long piece of tubing and run it backwards. That is to say, drop the stone into the Colloidal Silver and siphon off the Colloidal Silver into your storage bottle using the plastic or silicon tube.
This is highly effective and the stone is much easier to clean afterwards, than if you run the "impure" Colloidal Silver into the stone, as the impurities fall off the stone much easier. You will need one stone for each type of Colloidal Silver that you are making, as Ionic Silver Oxide must not be filtered using the same stone as the one you use for reduced forms of Colloidal Silver.