Converting sand base from freshwater to saltwater

[TnMark]

I'm thinking about converting my 135 gallon freshwater tank to a saltwater tank for corals and inverts.
My tank is very clean now with a 3-4 inch playsand base. The tank is cycled and well established for freshwater. Can I just add and mix in about 1-1.5 inches of lives sand for the substrate or are freshwater denitrifying bacteria different than salt.
FYI, I will at the same time add my live rock. How much base rock versus live rock do you recommend for a tank this size?
Thanks.

[TKOS]

The bacteria are different so the cycled tank you have now will have to cycle again.

[gcvt]

I would highly recommend emptying the tank completely and giving it a thorough cleaning before you add new sand for a marine setup.

If you're considering keeping inverts and corals, you're looking at a rather substantial investment in livestock alone, so starting over would be a wise idea. If you have problems with your reef tank in the future, you don't want to be wondering if it's due to the old sand - better to start off with a clean tank and a new sand bed.

[TnMark]

Thanks. That was my general impression but now I feel better.