i use a smaller bilge pump(500 GPH) for fine gold. a valve forms small ripples in the water. you want about 1/8 of a inch of water depth and as smooooooooth as glass surface on the water to save the micro peices of gold.anyway thats how i do it on my table. to much water force/pressure will blow it out. a pump on a blue bowl is a differnt story.use what they recommend.