Tough choice Woody. I've always thought that the 120 was about the perfect size for a reef. not too big, not too small, easily lit with 2X250 metal halides, great skimmer choices without breaking the bank, etc., BUT, yes, your tangs will definitely like the 180 better, and really, another 250 MH isn't THAT much more in cost, nor in electrical consumption...An ASM G-4 skimmer can be had for a reasonable price too. Probably my choice in skimmers if I were setting up a 180, (which I was 2 yrs ago, if you remember)...