cool, so explain to me how in my system, there is not a trace of valonia in the display tank yet in the refugium its become riddled with valonia now that the bulbs are getting yellow? same volume of water - same level of nutrients.
as the bulbs age, the kelvin reduces. algae prefer a lower kelvin, around the 7k mark. this is about the kelvin level of sunlight. aim for 10k or higher, preferably 14k. ensure your bulbs are not too old and still retain there intensity. same thing happened when i had T8's, as the lighting aged valonia started growing hard out. i removed the rock and scraped them and they came back. did the same, next time replacing the bulbs and no growth.