Quote Originally Posted by XSiVE View Post
just a comment; 48 LEDs over your 50g is going to be pretty high intensity especially if you're considering optics.

i have 72 over my 120 and have 250par in many spots on the sandbed... you dont need to worry too much about par
It's not really that excessive, XSiVE It's all down to the current that the LEDs are driven to. Is 48 LEDs necessary? No.

Tom, I think what may be best for what you are planning is to make the system modular. If you set it up so that each module effectively covers 1ft of tank length (don't worry about width, that will be dealt with in each module), all you need to do is add one more module once you move to the 90g. I think a 4x4 array (2" on center between LEDs per row, and 3" on center between rows) on a 10"x8" heatsink should do the trick. Build one and see what you think of it, then build the remaining units for the tank. The width of the two tanks are the same, so you shouldn't need to modify the modules once you change tanks. You may need to add optics once you move to the 90g to keep PAR levels up. 60 degrees should be fine there. No need for optics on the 50g. If you use XR-E LEDs, then adding/removing optics is a snap.