Help on my first water change. 10%

Its sometimes hard to properly convey information over the phone but I have to agree with most everything everyone else has said but also think the source of the fish is partially to blame. Most petco fish are already super stressed out or unhealthy before they are bought, combind that with a new tank and it's bound to cause problems. At least his ammonia is at zero now. As far as a cycle goes, it shouldn't be much of a cycle at this point considering he started the tank with live sand and liverock. Best bet is to get quality test kits and monitor the nitrites, nitrates and phosphates. If nitrates or phosphates spike and don't start going down, water changes with RO/rodi water will rapidly reduce them. Follow that with getting a good skimmer and rodi unit. Like we've already talked about. Don't get discouraged if you loose a few fish, inverts or corals in the beginning. In a perfect scenario we'd all start out knowing everything about the hobby and never hit a snag. Unfortunatly, this is a learn as you go type of hobby and it's increasingly difficult to distinguish opinion from fact.

I got the fish before I met Jason

Patience is key in this hobby and it so hard the first time you set up a tank.

Prime can help minimize the damage at this point. Maybe find a local reeder who you can borrow some seasoned media.... Most of us have media in our sumps for QT tanks.

"seasoned media" will add bacteria to your tank and help your cycle along. Most people keep things like some sort of sponge filter material or ceramic cylinders. When kept in your sump they eventually become colonized with beneficial bacteria.... when you buy a fish you can put them in a qt tank filled with water from your last water change on the "mother" tank and use the media to help prevent or minimize a cycle.

Prime is an ammonia detox chemical... Just add and it detoxifies the ammonia making it harmless in your tank. Think of it as a band aid, it doesn't solve the problem but buys you time to fix it.