Change substrate in established tank?

[Sealilly]

30 gallon tank been established at least 5-7 years and I suddenly wish to change out the substrate. Currently I have a basic gravel from a previous fresh tank and would like to convert to a live sand. Anything I should consider before removing gravel and adding sand?

[AlSimmons]

Removing the gravel in small sections at a time will be much safer than taking it all out at once. Maybe remove 1/3 this week, 1/3 the next etc.

The live sand can be added all at once.