There are a lot of examples when an invasive species takes over part of an ecosystem, decimating native species. However, no one notices the examples when a new species comes in and finds a good niche, making the ecosystem richer than it was before. I'd think that the positive instances would be more than the negative ones, because, the more diverse the ecosystem, the better it will be, in general. They must, of course, have a natural predator already present or they'll take over. However, we label zebra mussels, africanized bees, argentine ants, and carp as "introduced species" and then in our minds, all "introduced species" become ecosystem-wreckers.
It all depends on the niche that the introduced species can fill, and how it interacts with other species. The biggest problem is that you usually can't precisely predict how the ecosystem will react to the introduction of a new species, so you'll only really know after the fact... at which point it's probably too late.
So... release a predator of the cichlids at the same time