I have a all in one tank, 30x30x30cm, water volume about 27L/7 Gal. I have two Nemos, one Zoa, one Green Star Polyp, and one Sinularia. I did some water parameters test, and found out my ALK is 4.8, CA 300 and Mg 1320. Weekly wc, around 20-30%. Why my ALK is so low and my Ca is 300 despite there are no high consuming corals. My corals are barely opened up, but not fully. Is there something wrong in my tank that cause this low ALK and Ca? Or could it be something consuming the Ca, which led to the decrease of Alk instead?