To filter or not to filter

Hello all,

I started to add some nutrients for the plants in my aquarium (I got some
Dennerle stuff, don't know if this name is known overseas). Internal filter
in my aquarium (~63 US gal) has an active carbon layer in it. Instruction
for use of those nutrients say nothing about filtering the water through the
carbon, but I guess that the carbon should filter out the nutrients too, so
I have removed it from the filter. What is the usual practice? Is it true
that if I use in aquarium some chemistry I should loose the carbon filter?

TIA