Can if you want, but it would be better to leave it aside for when the carbon is actually needed IMO.
The carbon shouldn't remove the fertilisers, there are arguments either way but the general consensus seems to be that its no problem.
But you probably have no practical use for carbon right now anyway. So I would save it for when you buy new plants just in case they have been treated with copper and you dont want it to hurt your inverts.
Or maybe you will need to remove medication at the end of a treatment for your fish, save it till then.