Yup, you got it. As for how often to test, I would say once a week at first until you see ammonia starting to drop a bit. But, if you are like me, you won't be able to contain yourself to once a week. LOL
That is why I said the API are good for a start. They are cheap by comparison and will give you an indication of what is going on in your tank. They are not spot on but you will start to get a feel for it. When you think you have it figured out, run a batch of test and take the same batch of water to a store and have them run the same tests. You can then compare your readings to that of the store.
One word of caution, make sure that on the nitrate test, you shake the #2 reagent for at least 30 seconds EVERY TIME. If you forget to shake it one time and use it, the mix will be off and give you false readings. Think of oil and vinegar. If you shake it every time before putting it on a salad it is always the same. But, if you pour some with out shaking, it will never be the same again because you poured out more of than the other.
That is why I said the API are good for a start. They are cheap by comparison and will give you an indication of what is going on in your tank. They are not spot on but you will start to get a feel for it. When you think you have it figured out, run a batch of test and take the same batch of water to a store and have them run the same tests. You can then compare your readings to that of the store.
One word of caution, make sure that on the nitrate test, you shake the #2 reagent for at least 30 seconds EVERY TIME. If you forget to shake it one time and use it, the mix will be off and give you false readings. Think of oil and vinegar. If you shake it every time before putting it on a salad it is always the same. But, if you pour some with out shaking, it will never be the same again because you poured out more of than the other.