high alkalinity

Hello: I am new to reefing and have an Innovative Marine Fusion Nano 20 gal tank with skimmer and carbon reactor. It's been going for a couple of months. The tank has a lot of LPS, softies, and 9 small fish. Question: My readings are as follows: - NO3: 0 - Ammonia: 0 - Alkalinity: 12.3 to 13.2...