Hello! A couple things are about well water, sometimes heavy metals are in the water and if you have ever had a water test for your well, it would be nice to know if there was anything in the water bad for you or fish.
Copper is usually a problem for invertebrates. Do not over dose with sensitive fish.
As for using DW and S. moss for lowering pH, you have a couple things, you should do smaller more frequent pwc
, which is removing less pH lowered water at a time 10% 2-3 times per week for example, it keeps the pH more stable (you would need to know how much water to change and how much is needed for your tank). As opposed to 30% or 50% taking away the pH qualities, you have spent much effort to create, moss soaking and DW leaching tannins to your water.
By not changing your water very much at all, the plants suck up all the nutrients pretty quickly and then you have a nutrient deficient tank. Hoping someone here with better understanding and experience in using different things.
You are on the right track wanting to add some ferts. I don't do much fert adding (need to do a little more).
The other concern with well water is the possibility of heavy metals, you can use a treatment like Prime. If there is any question or known things in water with periodic testing usually done to make sure your water is safe. In Colorado there was so much mining in the mountains, sometimes there is arsenic or heavy metals.