RO water and the pH/KH/temperature fluctuation when water changes.

Could anybody share own experience how to avoid water parameter fluctuations while the water changing with pure RO water? I’m always afraid to add pure RO to the tank directly and mixed with tap water (4:1). But some people do. GH falling maybe is not so harmful as pH or KH. And increasing KH with baking soda (in few minutes) may kill all flesh.

Thanks

 

My purpose is to avoid using tap water and switching to RO+GH/KH booster. My desirable level KH=4dKH. But RO = 0dKH. To replace 50% by osmosis (and even more) I will have 2dKH (or less) so I need to increase KH from 2dKH to 4 dKH in a very brief spell. If I do that it may be harmful. Mixing osmosis and GH/KH booster out of tank is not a good idea as well, because one dissolves slowly and I need another volume I don’t have (and don’t want). That’s why I’m looking for an advice.

 

Is that enough for shrimps?

 

QUOTE FROM ADA EUROPE:

ADA All Rights reserved. Vendita Prodotti per Acquari d'acqua dolce - Takashi Amano NATURAQUARIUM

"As AQUA SOIL greatly reduces the pH, GH and KH values, it is important to use also tap water during the layout and the above-mentioned partial changes of water (around 30% every week). Hardness of tap water is variable. Advisable values are 3-4 KH and 6-8 GH. For example, we advise using 50% tap water, with KH 8-10 and GH 15-20, with 50% osmosis water. After about ten water changes, maintain a ratio of osmosis to tap water of 4 to 1. "