I think that perhaps water parameters aren't really that important, within reasonable limits that is. Further, most hobby test kits are blunt instruments and not really that accurate. In the UK our water standards are very strict, so if it potable it's got to be OK for our critters and plants. Most of the fish we buy in the UK have been bred in similar water conditions to those in which they are kept, eg hard water. And densely planted biologically stable tanks are well documented, albeit anecdotally, to absorbe metabolic wastes very efficiently. So water changes aren't always needed on a regular basis. Similarly, I've kept Hi-energy tanks that also didn't need frequent water changes - every 1-3 months or so were fine.