For what my two cents are worth. I agree with hdtran. water changes are your best bet. I'm surprised your ammonia shot up so quick. I haven't added any fish yet, still waiting on my second shipment. but the amount of crabs and other life in the tank has got to be producing waste (ammonia). Spent about an hour last night lwatching the live sand. there are so many critters in it that it's hard to take your eyes off of it. Sorry for the late reply, but I'm only on line at work right now.
Keep us posted Landlord.