Changing substrate from gravel to sand

[albwalbw]

I know this question will have been asked a millions times,however I really don't want to kill any of my fish/shrimp.I was thinking that I would take out half at a time as its only a small tank what do you guys think? I have a fluval edge so 23l and its planted, what sand would you recommend and what Would I need to put under the sand if anything?

Many thanks Dan