heres a list of PAR/PPFD values to help decide, you are gonna need something with some *umph* to it since the tank is 24" deep. i only listed the ones in the 14k/15k/20k range. obviously most 10k bulbs blow these away in PAR/PPFD
Icecap ballast 250w
aquaconnect 14k = 406 PAR, 83 PPFD (AWESOME bulb/ballast combo)
hamilton 14k = 352 PAR, 69 PPFD (next best thing)
radium 20k = 330 PAR, 66 PPFD
coralvue 20k = 307 PAR, 60 PPFD
XM 20k = 270 PAR, 53 PPFD
coralvue reflux 12k = 51 PPFD
PFO HQI 250w ballast (bulbs dont last long)hamilton 14k = 420 PAR, 99 PPFD (10k look)
radium 20k = 395 PAR, 85 PPFD (14k look)
coralvue 20k = 355 PAR, 91 PPFD (14k look)
XM 20k = 314 PAR, 79 PPFD (14k look)
coralvue reflux 12k = 74 PPFD
M58 250w Magnetic ballast
XM 20k = 73 PPFD
aquaconnect 14k = 62 PPFD
XM 15k = 55 PPFD
hamilton 14k = 53 PPFD
coralvue 20k = 52 PPFD
Icecap ballast 400w
aquaconnect 14k = 143 PPFD
helios 20k = 119 PPFD
coralvue 20k = 112 PPFD
XM 20k = 99 PPFD
hamilton 14k = 80 PPFD
radium 20k = ????
PFO HQI 400w ballast (bulbs dont last long)aquaconnect 14k = 170 PPFD
helios 20k = 149 PPFD
radium 20k = 147 PPFD
hamilton 14k = 140 PPFD
coralvue 20k = 146 PPFD
XM 15k = 114 PPFD
XM 20k = 98 PPFD
M59 400w magnetic ballast
XM 20k = 128 PPFD
coralvue 20k = 110 PPFD
XM 15k = 104 PPFD
hamilton 14k = 96 PPFD
helios 20k = 96 PPFD
radium 20k = 90 PPFD
aquaconnect 14k = 80 PPFD