I am building 2 300 gallon fish tanks on a double rack stand. I am planning on having the top overflow flow into the bottom tank and from the bottom tank into a large sump (dont know how big yet). I may drill the tank but, if I dont I will be getting an overflow box. I like the CPR CS models but, the max GPH is 1600 gallons per hour. I feel like this isnt enough flow for thus tank. The stock will be- TOP TANK- 2 rays and a few other odball BOTTOM TANK- Will be divided for 2-3 flowerhorn. What overflow box should I get (dont want a siphon tube) is 1600 GPH enough flow for such a big tank and such a heavy stock?