When placing frags onto a frag rack, make sure to pick them up and possibly move them around from time to time. As the coral frag sits in the same location for a while, it will not only encrust onto the frag plug, but it will also start to grow onto the rack itself. This isn’t a huge concern for most aquarium keepers, as the coral can be easily removed from the rack at any time. Unfortunately though, it will break the coral, leaving some behind on the the rack. Again, not a huge concern, but the coral can eventually take over a portion of the rack and even encrust onto nearby corals, which could potentially kill neighboring corals depending on which species are coming into each other’s proximity. On the flip side, this could also make for an easy way to propagate some fast growing, encrusting corals, as empty plugs can be placed on the rack and the coral will over grow them as well.