i use the smallest aquaclear filter on my tank for circulation and a refugium. i think you can get them from petsmart by printing off the sheet off of their web site for under $20. creates good flow, can hold the heater so it's out of the display, can hold extra rock rubble, and is clear so light can shine through for chaeto.
i'd go with about 3lbs or lr - small pieces and then 1lb or so of rubble for a refugium.
don't forget salt and RO water.