Is it true that now we don't to add Sodium Bicarbonate to our planted tank after a WC ?

Yes, some folks do if their KH is low, say less than 2.

I never bothered and have never seen any adverse effects over many years.
If you have Rift cichlids etc, then yes.

Regards,
Tom Barr

My KH is 0 out of the tap and I stopped using baking soda about 6 months ago. Plants are doing fine. With a high fish load and a not so efficient filter I have pH crash issues if I don't really keep on top of the gravel vacuuming. Doesn't appear to have any effect on the plants though or even the fish so far for that matter.