A little off topic, but couldn't resist to say.
Discus are some of the least eco-friendly fish you can keep, aren't they?
Unless someone in using the daily waste water(from water change) in ground water recharge, watering the plants, recycling it again effectively, you just can't justify such enormous wastage.
And of course I can say with confidence almost all discus keepers if not all don't take the above measures.
And this is excluding the water wastage from an RO system, if we include that it'll be like atleast 5 litres for every liter used. In case of a 200 liter tank which is bare minimal for a discus you waste like 500 liter of tap water to create 100 liter of RO water per day, 100l by itself is a big figure over a year if you think about it.
That's one of the prime reasons I stayed away from them. I stay in an apartment building and I don't have ways to efficiently recycle water from huge daily changes. And unfortunately discus happens to be a sensitive fish in that regard, you just can't ignore its demands. And also there are tons of other things you can do in this hobby if you just ignore them.
I don't mean to discourage discuss/soft water fish keeping by any means, its just that we should plan ahead and be a little more responsible.
It doesn't sound a big issue for now but with our growing population its inevitable, even at present there's huge water scarcity during summer time. So why not we address this wastage issue?
Ours(proper fishkeeping) is still a small community and it won't take much time to make conscious efforts.