Hi Richard,
No idea on the micron filter sorry but I will say this, I had discus over 12 months ago for the first time keeping them. Now it could have came down to being very inexperienced, but I also read somewhere that you don't need carbon in fresh water tanks or with discus. Now, I had 5 discus die over time in my 4 foot tank that had no carbon running in it, they developed all types of illnesses. Since then I have read up seriously on carbon itself, it is actually very important to use it in fresh water tanks as it removes nasty toxins from the waters, BUT it must be replaced every 3-4 weeks with new carbon. Unless you get solid advice on this site about not using carbon I would be using it, I'm only new here so I'm yet to see a carbon topic. Your best bet is to read up on it online. Just my 2 cents worth on that note