As the title says I had to temporary replace 1 of my Radium bulbs. I noticed a crack in 1 of my Radiums while cleaning the tank this week so I had to replace it w/th a XM 20K until my new ones could get here.. AND IT SUCKS SO BAD !!!!!! There is day light and dark difference between the 2 bulbs the XM just flat out sucks compared to the Radium in my opinion.. The pic dont do it justice on how dull the XM is (XM ON LEFT RADIUM RIGHT)