It all depends on the type of algae you have in your fuge. At the ocean's surface the K temp rating of sunlight is about 5800K. Most green algae will do just fine and will grow well with a K rating between 5600 and 6700K, the usual planted tank ratings. Red and brown algae are adapted to deeper areas that have a higher percentage of blue light so something around 7100-10000K would be good for them.
Hope this helps,
Phil
