I have a plastic 55 gal. sitting around that I could use, how much flow do I need going through? I have some Rio's sitting around that don't use to much juice. Can I use something like Lava Rock instead of balls? Like a dummy I gave 20 gallons of them away last summer.Zoodiver;4235121; said:I can take some. All you need is a 5 gallon bucket (or 40 gallon Brute trash can), drill a bunch of holes in the bottom and have it above the tank or sump, so the water flows in the top and out the bottom.