So I finally decided to change the lightbulbs in my aquarium-lamp. According to the book you should change bulbs once a year, but I have now waited for about 5 years, partly because the bulbs are so expensive and partly because I do not have any corals (except for 2 dead ones) or other inhabitants that are very much in need of a correct light temperature or intensity. For two 250 W 13000K bulbs I paid 1750 NOK (~210€ ). Hopefully the higher (more blue) light temperature will make corals feel better than they did the last time I tried and hopefully the algae will like it less. The previous bulbs were 10000K. For reference the color temperature of a candle flame is about 2000K, the sun about 5000K and the sky 8000-10000K. So 13000K is pretty blue. By the initial definition it is the color that a block of carbon would glow with if you heated it up to 13000K (12727 ℃ ).
Changing the bulbs took me about an hour, becase you need a ladder to reach the roof, then you must make sure that you are steady on your hands so you do not drop the entire lamp into the saltwater. By yourself it’s a small challange, but it all went fine.
By the way note that I use real unicode chars for both Kelvin and Celcius. K is different from K, and ℃ is different from °C =) And by another way it’s not called a degree centigrade it’s called a degree Celcius since 1948!