I don't believe the ammonia reading. What test kit are you using? I'm pretty sure it's giving you a false positive. A healthy reef setup will have a zero reading (even with a high bioload). If your tank had ammonia in it your SPS wouldn't be so apt to look as good as all that.
Ever test for NO3 or PO4? With the 24 fish I'm going to guess the NO3 is non-zero but even just eyeballing the tank I would expect it to be fairly nominal.