High axle: RO Water - you know that cannister under your kitchen sink( PURA TAP)for drinking water , thats it. Reverse osmosis is the process of remove heavy chemicals and Metals(I think)out of the water, You can actually get RO Machines costing millions used by government departments - then you get the $120 version for you're house which does the effectively the same job.
I've never tried this but have read of people using RO water as a substitute for rain water- @ water changes using 50/50 tap and RO is meant to great for inspiring spawnidge.
I don't think it is a very difficult process ,so anyone else fell free to add what Ive left out or correct me if I'm wrong.
Or have a quick goggle- you'll find it straight away