Is it possible that the bulb u replaced the first bulb with......was doa?
I've got the same fixture(I'm pretty sure) and I haven't taken out the ballast but I did crack it open to mess with the noisy fans.
There are four screws on the end caps, that's all you need to remove to get in to work on the fans anyway.
LWB........how was your experience with aquatraders?
And on a side note..........how deep is your tank?(I know your having good(growth)luck with this fixture)
I've been reading alot about CF
and how it doesn't penitrate as deep as T5.
I'm wondering if this fixture is enuf to grow glosso in my 25" deep tank.