I'd get the Keys rock from LR
.com over the Gulf rock. more colorful, and you'll still get critters. plus the keys is aquacultured, which seems like it'll have some more interesting shapes.
also, a lot of people find that LR
.com rock doesn't need any curing...they pull it from large holding tanks, pack it and ship it and in 20 hours you've got it with next to no die off.
the most ammonia I had was .25ppm, and I'm told my ammonia kit sometimes reads false positive for ammonia.
If you do order from them, call first, and talk to Mike about your tank. If its new, without any rock, they'll select larger rocks to help you build a foundation. If you're adding rock, he'll ship smaller pieces to help you finish it off.