Wait a minute... I dont know whats scarier... That this website exists, that there is an exact answer to this question, or that Moe pulled it out of thin air like that...
Heheheheh.
I have been using that service for at least a year now. I shoulda told the Boston reefers, I guess.
I love that it can act as a memory bank for my test results (1 year and counting), and when I last replaced my bulbs.