I currently have a 220 gal. I'm making a home made wetdry out of plastic drawers i picked up at walmart. I've made 2 overflows out of 1"pvc. I'm going to be stocking this tank with some large SA cichlids. How much water flow do I need to have? I've heard many diff things from 3 to 10 turnovers. I've heard the Magdrive pumps have good value. I was looking at the Mag 18 and the Mag 24. Any opinions?