I'd like to see a pic of you planted haven
. Can you tell me more of your system and your maintenance/supplement routine?
There are many ways to augment soft water parameters, whether it be off the shelf to everyday household products. Baking soda will add to the carbonate hardness and epsom salts to add to the total hardness. Some even use synthetic sea salt mix, ie Instant Ocean(TM).
Having live plants in the aquarium definitely moves to the direction of a self sustaining system, but again, another entity to keep happy and thriving. Of what I read in various aquarium forums and clients that I consult, +95% of all new aquarists begin w/o live plants.
With wet-dry/trickle filters for denitrification, I'll have to disagree on the denitrification process as their primary function is for nitrification and gas exchange. Denitrification only occurs at the sponge block after the bio-tower or the bioballs that have a centre compartment w/a sponge core where there will be an area of low oxygen. A plumbed freshwater system w/a wet/dry filtration system will add at least $800CDN including a submersible pump.
Making a vegetative filter will add to the dynamics of the aquatic system. Depending on the scale that one wishes to create:
http://www.breathingwall.com/
Perhaps I'm splitting hairs on the terminology o.O but making my hobby into a career I hope to help dispel them and come to a middle ground where everyone will understand and appreciate the complexities that make it all work.