Quote Originally Posted by keith_r
when figuring the size of the sump, it's a good bet to use 50% volume of water.. you want the sump to have enough capacity to flood the growbeds and leave water in the bottom so that the pump isn't sucking air..
i'd be more comfortable with a 250gal sump, but thats just me

Point well taken. I only used 25% as a minimum, not know what gravel he was settling on. On my own system I measured a gallon of media and measured how much water it took to fill it and extroplated to the size of the GB.. I wound up a little less than 40% with my media. I did forget to add enough to keep the pump under water huh?