Here is the latest on the LED marine coral experiment.
We will keep a photographic record of the light comparisons, but it is unlikely that they will show growth differences in only a month (maybe 2). The corals will have changed color in that time period (even when photographed with flash) This reversible color change occurs within a month, and we are using it as evidence that the corals have adapted to their lighting. Additional anecdotal evidence is accumulation as well. About 25% (6 colonies) of Galaxia under LED for 4 weeks now have entered an aggressive growth phase. This is indicated by the production of large sweeper tentacles that digest neighboring coral. None of the Galaxia (400 colonies) under VHO or Halide are showing sweepers. All of the corals are in the same water, at the same temperature and flow rate. Only the light is different.
Marine Aquarium LED Study 