What blue filter pieces? They aren't the biofilter bed are they? The only thing that should be removed is the carbon when using such medicines as M-Green.
I have to agree with SumpinFishy - When I first started out keeping fish and used such medicines I had my hand in the tank all the time during treatment, just wash your hands. I am pretty sure that research is assuming ingestion of the chemicals.
And I know everyone everywhere is still saying put salt in the freshwater tank for ich but it really isn't all that good an idea. Many fish species are sensitive to salt (like plecos) so one should be aware of what their species' tolerances are. Also the salt works against ich by basically stressing the fish so that it exudes more of a slime coat which helps to keep new parasitic cysts from attaching while the amount of salt necessary to actually kill off the free swimming form of the parasite is too much for most freshwater fish well being. I haven't had a case of ich in quite awhile thank goodness but I would use nothing but Mardel's Coppersafe.
By the way with these M-Green based meds usually the instructions direct the treater to do waterchanges when the med regime is done and these along with the replacement of the carbon will get rid of the medicine (though it may permanently stain the tank's silicon seals green or blue.
Cheers
