Rock will bring in some pods. If you have a reef ready, or external overflow, you can set up a refugium (low flow, no predation) with some chaetomorpha and other macro algaes and provide a breeding ground for them that will constantly replenish the display. Reducing predation and giving them a place to live (even if in the tank) without being washed away are the only surefire ways, IMO. They do have the HOB fuges, too, that would provide similar conditions to a fuge (just not on scale).