ive had them all over the tank,they spread and grew and have left behind lots of little colonys. The blue ones have not done well. Whereas the others have especialy one colony which they no longer seem to sell, has outgrown all the others.
Id say they seem to prefer more rather than less as when I turned the lights down some time ago they lost a lot if thier colour,since I turned them up thier happier. Thier in a moderate flow area. Out of the main punch of the lamps high up and directly under two inches off the sandbed.