I think LiveAquaria is a good choice they are probably the mose reputable supplier in the hobby for sure. I bought my first live rock from them and used it to cycle my tank. Using live rock to cycle your tank is way better than liquid ammonia or fish food to cycle your tank because you get the bacteria colonies that come with the rock and the dead stuff creates the ammonia to grow whatever bacteria didn't die during shipping. Just put it in your tank with fresh RO
saltwater and watch the cycle process with your test kit. About 4-6weeks.