Ok I should say up front Im not near as brilliant as you fine folks, I was a C student now Im a Dad that cant figure his 11 year olds homework out :yuck:. I hope someone will be so kind as to help me lol. Scenario: We are going tuna fishing, so we need a live bait (anchovy) tank. This requires a 30 Gallon plastic rain drum with water flowing in one circular direction to create the needed "current" to make the tuna bait happy. If anchovies are not swimming against current they will die. I am guessing around 2 MPH in a circular motion. This will be created by a water pump hooked into a pipe that is mounted vertically in the drum with holes drilled in one side on the pipe hence creating the current. My question: Is there a formula for figuring out the needed GPH pump, vertical pipe size, and size needed for the holes in the pipe?