You need to remineralise to proper parameters for what you want to keep.
part is not necessary for much,which is nice since it is always spent faster then other filter components.
Many use a simple product like seachem equilibrium;
Or seachems replenish;
I remineralise with calcium(kent turbo calcium),baking soda and Epsom salt for my GBR.
I use a HM TDS
meter and an appropriate amount of each to get the water where I need it.
There are other recipes also!