My tank is 25 deep too (should be more than from the light to bottom of the tank) - And I am lighting it with T5's
Let see how's thing doing in there.
It was a big debate for me when choosing the light but I finally go for T5 after reading some articles about the MH related to over heat and chances of fire
I love MH though but have to stic with T5's for the sake of safety and summer's heat concern.