48"l, 13"w, 18"t, and the light sits 7" above the water
Hi, what is the color temperature fo the HQ lamps (Kelvins)? You might as well put them 1 foot, maybe more above the water. Metal halide bulbs are quite powerful. Probably some testing/adjustements to do, and the color temp must be in a range for freshwater plants.
If you had enough light for a reef tank you now have way too much for a planted tank, unless you are raising the lights much farther above the tank. The color temperature of the lights is probably not very good for a planted tank either, if you are using the same bulbs.