A 65g tank... I assume 4' long? Which fixture are you looking at? A 4' tank may need more than 1 depending on which one you are getting. And if you get a good one, you don't need to get another one later with Cree leds. They are very good, and if you are doing a DIY you can cut back on how many you need, but you pay more (for the current product). But any fixture that is using other leds like Bridgelux works just as well in terms of the quality of light it gives off. Crees are just more efficient. But if you run a Bridgelux fixture at 70% power, do you really need a more efficient led?
