An easy-to-answer newbie questions

[Kelpie]

Why is MH lighting frequently supplimented with actinic? What is the correct balance? Finally, why is actinic supplimentation unecessary with 20 K MH?

 

Thanks

[wolfpac]

Usually atinics are used to balance out the yellow look of halides. Atinics also causes the greens and blues of fish and corals to fluoresce and are usefull in the whole light absorbtion by corals thing. 20,000 K bulbs are bluish-white so they don't need to be supplemented with atinics. 10,000 K is crisp white, and 6,500 is the lowest you can go with reef tanks and is yellowish. the most common used balance is 10,000 K with atinic.