The fact of the matter a dutch style tank will be impossible to do in a 55gallon. At least as far as my mind can see. I think getting some branchy wood and trying to accentuate the length of the tank would be good. Look at tsunami's 20gallon long and maybe ryuken's tanks for some pointers. I am sorry to say that i think you should lower the amount of light on the tank. 260watts over 12 inches of width is a lot.