What else should I be testing?

[Myka]

When you're busy stocking a 180 gallon tank I would highly suggest the use of a quarantine tank. Not only will you really appreciate that new fish after waiting 6 weeks to introduce him to your tank, you will be almost eliminating the health risks to the fish already in your 180. A 180 gallon tank can hold a significant dollar value of fish, and protecting that investment would be a good idea.

If you're really having troubles double check your test kits with a sample taken to your LFS.