[helene schoubye]

I use 100 procent reverse osmosis water and have done for a long time – with the paro’es. As you say, there seems no reason to add tap water as you would normally.
When I started with paroes, – and also still when I talk to other aquarists about soft and low ph water, the generel idea is that it is almost dangerous to use 100 procent osmosis water, and most people would really not recommend it. But with paroes its different, this is the water they are used to, – so much better to use this as it is. And if you take precautions and monitor any changes or big leaps in ph etc – then theres no problems really.
I have actually never experienced any of the problems that I was told would be present by using pure osmosis water, – (ph-crash among other things)