Welcome to your new addiction!
Welcome to the MR family! I think you will like it here. Really nice people around.
You have gotten very good advice already in all the previous post. I will only add that you need to get better test kits, such as "Salifert, Elos, LaMotte, Hannah Checker" to name a few.
I use API only for a quick ammonia, nitrate, or PH to compare to my hand held PH tester.
Aren't all those test kits and testers a bigger investment than my entire tank?