You probably already know this...But here's a quote from a link....
Don't forget that to grow a strong purple coralline algae (purple, green and red rock growth) you must have the necessary lighting consisting of 4watts per gallon of water as a rule of thumb and necessary trace elements of Iodine, Strontium, Molybdenum and liquid Calcium! These are the big trick all the true reef and saltwater hobbyists growing extremely beautiful live rock are doing and understand!
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SETUP-3Reef shirt&bumper sticker,90gal Tank, 250 watt Heater, . 40lbs live sand , 40lbs L/R - 4x65watt PC , Mag12 return pump, 30 gal sump/fuge
FISH-1 Blue Throat Trigger,1 Yellow Watchman, 2 Green Chromis,1 Maroon clown,1 squirrel fish,Lawnmower Blenny
CORAL--Purple Zoanths, , Toadstool , Finger leather, Trumpet,Star polyps
INVERTS-2 Feather Dusters,1 bristle star, 10 mixed snails, 15 blue leg hermits,2 Tuxedo urchins | 
The Rock has Landed! 
