Changing The Substrate

[Dinothefish]

Need some Advise on Changing My Sand Substrate To The Black Sand Substrate How should I Change That out Without Over working the Process?

[ScottieB]

Totally doable!
How big is the tank and how much substrate are you removing? What about fish population? 

But, not knowing the details though the general idea is to provide more surface area for biological filtration while your switching out gravel. 
 

 I would start by adding an extra sponge or biological media, leave it in for a couple days or a week.  Then start removing your existing substrate. Say… 20% once a week? (Could be more aggressive depending on your biomass and existing filtration). Once your old substrate is all gone, rinse the new one real good and put it in gently so as not to cloud the water too much. 
 

The slower you make that kind of transition the better but the principle is your gonna be removing a lot of biological filtration so let the population of bacteria shift slowly. 

Hope that helps!