Nanocube Filter to Fuge

[Puffy]

ok, since back in the back of the nanocubes are the Wet/dry filters that suck for salt walter, i'm going to leave the stock pump and take out everything in the back even the sponges and put them for my 55 gallon fresh tank. but i'm going to cut out a section of the hood and add a light to that so the back will have light and will be a FUGE! lol I know people have done this before, but what kind of cheap light will i need for it? One that will be enough light but not enough to heat the tank, i am thinkin of makin a little canopy (MAYBE) i'm just going to fill the back full of lr rubble and bout 2 or 3 inchs of sand.......i want my fuge to rock! lol any ideas on this please let me know caz even though i said NO MODS i got to have some! lol anyways thanx Oh and i'm going to be makin like 20 lbs of cement rock for the tank and with the LR rubble in the back will taht seed the front (cement rock) or will i have to add the rubble to the main tank for the time being? Anyways tahnx!