all "soft" corals conduct chemical warfare - it's how they defend/spread. greater amounts can be released if handled, fragged, etc. shouldn't be a problem.
as far as growing like weeds, use them for frag trading. put rubble in the direction of growth [usually toward light source], it will spread onto the rubble, at which time you can cut it away with a razor and trade with other reefers and/or with your LFS