Since you have a 55gallon, I saw the guy that sells frags put 2 of #3 into his 75 gallon. so I think you might need only 2 #2s instead of #3.
Sorry Frankay... and if I'm right, someone made a diagram, wasn't it u? put both towards the back on the left and right and shoot to the front that's how I saw them... there's a diagram somewhere in one thread, gotta search for it.
28GL BF, Hydor Koralia Nano PH, AquaClear 50 with LRR, 24" Nova Extreme T5HO, 20Lbs LS and 35Lbs LR