the best way to use the silver magnet is the 2 fix bath method. use a clip of film and time how long it takes
your unused fixer to clear the film. double that time for your total film fix time ( prints need to be fixed for the manufacturer's recommendation )
so that means the clear time for 1 bath, and the same time for bath 2.
when it takes double the original test time to clear the film clip your fixer is ready to de-silver. make a new fresh bath for #2, the old #2 becomes #1 and keep an eye on it ...
they say you can keep re-using the fixer after you de-silver it, but i have never done that so i can't really recommend that ...
you submerge the silver magnet in a non metal* tank/tray whatever you want to de-silver in ( a plastic dollar store shoe box works great )
and when the light changes from dim to bright you are done ... you can keep an eye on the cathode when it plates dark-stuff you are done.
there is still about 50 parts/ million silver in the de-silvered fixer. you can run it through steel wool or aluminum foil or copper flashing or whatever you want
to get the rest of the silver gone, and dispose of the spent fixer according to your local regulations.
i also sell trickle tanks to remove the rest of the silver ( in your fixer ) from your waste stream. it will de-silver your wash water and the fixer already put
through the magnet ( the magnet / electrolytic unit is for high concentrations of silver, the trickle tanks/ion transfer is for low concentrations ) used with
the magnet they last for 1000 or 2000 gallons of fixer/or wash water ...
its best not to dump fixer down the drain, the silver kills the beneficial bacteria in sewer plants and septic systems will corrode your pipes and end up
in your garden or well or ? ..
yup they say 99% pure ... the 1% probably accounts for black stuff you might get on your cathode when you leave it on too long ...
let me know if i can be of any more help !