Probably won't matter much.
If your tank EVER shows ammonia, that is a bad sign. Once a tank is cycled, you should never see any ammonia.
Here is how you get a new tank going. 1st, you do the initial cycle. That means you should be able to see the ammonia rise and then fall, see the nitrites rise and then fall. They should then both go to zero. Then you can add a fish. Adding a fish will cause another cycle, though smaller than the first, while the bacteria poulation grows to catch up with the new bio-demand. So, don't add another fish for 4-6 weeks. Then, when ammonia, nitrites are zero again, the fish is free from disease, eating well, then you can add another fish. Guess what, another mini cycle occurs, so you need to wait it out again. Repeat as necessary. Remember, when going from 1 fish to two fish, you double the bioload. When going from 2 fish to three fish, you increase the bioload 50%. etc.
Tangs are very active fish, create a lot of bioload, need a lot of space, and are very prone to getting ich. Not a beginner fish by any means. Also, probably should have 1 max in your sized tank.
