I have been keeping sps for a while now and they have always been fast growers, very colorfull with great polyp extension. I have recently started adding to my zoa and paly collection, but unfortunately Im not having the same success. Any way, they dont seen to open all the way and some of them are even melting away. I have a 450 gallon reef that is 30" deep. Most all of my zoas and pallys are on the bottom of the tank. I am running 3 400 watt metal halides with 6- 4ft t-5's. for flow I am runing 2 tunze 6200 and 3 6201's. I dose reef advantage calcium along with baking soda. My alk drops from about 10 to 6dkh in the period of one week but my calcium rarely drops under 420. Any advice would be greatly appreciated. thanks