Actually potassium sulfate is a mineral that is mined naturally in Utah.
Ya mean stuff that comes out the ground is naturaal?
Organic aquarium ferts is a bit an odd thing.
It's the organic fractions that harm the aquatic ecosystems in many cases, NH4 and organic loading.......at least our tanks.
We use NO3 in the inorganic forms as well as PO4 to avoid algae blooms and fish toxicity to remove the organic fractions through rapid oxidation by the plant's and rapid uptake of NH4 produce by fish waste.
So yes, the tank is very organic, you might consider certified organic fish food as well if you believe this to be an issue. Organic free range worms Rex?
You know you cain't sez no!
Other methods such as a non CO2 plant tanks uses soil in some cases and fish waste to supply the tank, that might be more your tune.
You can use organic ferts, but you need to mineralize them good, boiling for 10 min or soaking for 2-3 weeks in shallow tray of water will leech the NH4 out.
But if you claim to be doing this for organic reasons, you need to make sure the fish waste/food sources are also organic. Non CO2 also provides non water changes, so you use less water as well.
There are trade offs associated with the various methods, but that's up to you and your goals there.
All in all, it can be done pretty easily, but you will end up using the non CO2 method, not a CO2 enriched method, as that goes directly against the concept................