Now that I am done cooking...and eating steak,lobster,crab....and shrimp, I will respond. Honestly I am still stuck on needing 4. I agree that it can be done with 3...and for that matter 2?
Mike did show me how 3 would get pretty good coverage but also agreed that Idealy it would be 4. For my last attempt to explain why I don't like the idea of going with only 3 I will say, You have roughly a 11x16 inch fixture. to run them all lengthwise across a 36 in deep tank is relying on the 11 inch wide side to light that 36 inch area. if it was a 72x24....or even 72x30 I would be fine with 3. perhaps even a 6 puck in the middle and two 4 pucks on the sides.
Bottom line is after one spends the many thousands of dollars getting a larger tank up and running, I'm not gonna skimp on the last $369 Especially when it comes to the lights! makes no sence! Spread them out and run them at less power. more even coverage. right?