Personally I would steralize it in bleach before adding it.
Now I have done this so don't flip out and let the word bleach scare you.
First get a bucket, doesn't have to be perfect, you'll never use it again for saltwater after this.
Put the rock in the bucket and fill it with enough water to cover the rock. Add bleach. I used a couple cups of bleach to 3-4 gallons of water.
Let it sit for a half hour. If it's not very white mix it a bit and add more bleach and let it soak more.
Take the rock out and rinse it in either a washtub or spray it with a hose for a while, really try to get the bleach off.
Then I added it to another bucket with some waste water from my RO/DI machine. Let it soak overnight. Dump it out the next day and add more filtered water (plain tap might work as well, I don't see why not).
Do 100% water changes on the rock daily for a week.
The last 3-4 days you can add a dechlorinator to the water to pull the bleach out of the rock (something like Prime works).
So after a week of 100% water changes and soaks you should have stark white live rock. I let mine dry for about 3-4 more days and gave it another quick rinse and added it.
You can see the first piece I tried here under the clown:
I ended up doing over half of my rock in stages due to a bubble algae outbreak. If done right it is 100% safe.
The other alternative is "cooking" the rock and that will take a month+.
