i use to use PH Down. but it got expensive. (rember keeping discus means 50% water changes...) and that $5 a week for a bottle.
so i gave up on that. I kept 6 discus just fine in my 55gallon. But now im down to my pair that paired up (also for sale, planning to grow out the fry in my 55gal).
As for the breeding. It takes a while (almost a yr) for a shoal to bond and form a pair. then a lot of trial and error for them to get it right. then, you have to start using RO water to make sure the hardness is low for the eggs to hatch. then when they do hatch you have to buy bbbs. then when the fry grow you have to feed them beefheart or other frozen foods, etc... and u have to feed them 6 times a day... it costs a lot of money and time to breed. I change my fry tanks water 50% daily (minimum).
from my experience, they are not so hard to care for. they eat do change their minds alot on food though. once tame, u can pet them while feeding.
water, i just use tap water. it's slightly hard water. but they thrive.