Your recommending 0.5 watts of LEDs per gallon. Would you mind converting that to mcd per gallon. I am looking at 2 LEDs:
1600 mcd / (1.85 V * 0.2 a) = 4,324 mcd / watt
2800 mcd / (1.7 V * 0.3a) = 5,490 mcd / watt
You will not neither of these are 1 watt
. But one produces 25% more light. Don't you love the LED efficiency it makes picking the right one that much harder