Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Activated carbon has a good affinity for more complex molecules, so chelated ferts are likely to be removed from the water. The simple ferts (KNO3, KH2PO4, K2SO4 and most traces) are not removed from the water in amounts great enough to be a problem.
Driftwood, roots of trees and similar materials has no noticeable effect on fertilizers. These materials may release tannins, and this can lower the pH in the tank. This might affect fertilizer availability.
Boiling rocks does nothing about their chemistry. If it is a limestone rock when you put it in the pot it will be a limestone rock when you take it out.
Boiling can help if the rock came from a wet location (lake, river) and you suspect it carries diseases or parasites. Chlorine bleach cleans these rocks of diseases and parasites, too. (Then rinse and soak with a double dose of dechlor. Air drying will also allow chlorine to evaporate)