Buck I have been looking at the pictures of your 5g nano planted tank and first let me say that is a bad ___ web page. What do you use to build something like that, is it some software you can download off the internet?
And, in looking at the detailed pics of the setup Id like to make a few predictions. This system is already very aged in terms of microfauna and bacterial colonies that are adjusted to this type of substrate-a good thing. One thing this nano will have that few nanos have is a sandbed rich in organic material, not necessarily raw fertilizers such as bulk phosphate but compounds and elements locked up in bacterial, animal and plant matter all at varying stages of decay.
This rate of decay is what releases the critical nutrients for algae buildup, so thriving plants should compete for much of it in the water column. A denser stocking of fast growers such as val may help to pull nutrients out of the water. In this setup, Id predict it would be favorable to limit water permeation in the sandbed to keep its richness to a minimum in the upper column. Once you have a decent root matrix (if not already) aerenchyma from active plant growth will keep the soil healthy, minimizing anaerobic patches.
When I build another nano I want to try rich organic soil like the type you have found---already accustomed to life underwater. This will hold a massive amount of trace elements, dosing will be almost nill Id suspect/great tank bro this type of nutrient supply is just what a planted nano needs--all natural and quite a store for the volume in question....