ahhh,
refugium set up...
here is a video of chaeto growing in a 5g bucket receiving 600 gph flow in a circular motion to encourage rolling for maximal growth. it is lit by a 65w 6500 lights of america fixture.
the bucket chaeto water then flows out of its drain pipe down the length of the barrel and then flows up out of the top drain in the blue barrel.
in the barrel is probably about 400 pounds of live rock. it is lightly aerated for gentle circulation as well to prevent dead spots. this is to encourage sponge and tunicate growth used in filtration. thus, the barrel is circulated with no pump impellers.