Will 20K bring out more colour of corals?
 

It looks like lots of people using 14K for more balance. Will 20K bring out more colour of the corals, but slowing down the growth?

Before I jumped on the T5 bandwagon, I ran only 20K metal halide bulbs. The colours of my SPS were always amazing but the growth rate was indeed slower as 20K bulbs have notoriously low PAR values compared to 14K or 10K bulbs. Many people don't like the blue-purple colour of their tank under a 20K bulbs as well but its all personal preference.