Planted Tank Guru
Join Date: Nov 2009
Location: Missouri united states
Plant's will begin to do poorly and show deficiency symptom's if nitrates(nitrogen),become limiting.(Is needed macronutrient)
Plant's can use the break down of fish waste,fish food to receive some ,but it may or may not be enough for your tank ,or my tank,or John's tank.
Rather than add more fish or more food to closed sysem,I would opt for adding small amount of all macro/micro nutrient's in the way of the dry mineral salt's from someplace that sell's fertilizer's for aquarium's.
AquariumFertilzer.com, GreenleafAquarium's.com are a couple places I have purchased them from.