Help building a LED fixture
Hey guys so I have found someone who will be able to make me an LED fixture that I will use above my main display tank that is 30x18x16 inches lxbxh. It will be a dimmable fixture which I think is important in an LED setup. The fixture will be using 3W Cree XPGs. I know all my questions are inter related but Ive broken it down to help me understand better :
1] How many Watts do I need for a Med to High (dimmable) light tank ? Right now I am thinking 18 LEDs for a total of 54W
2] Placement : Im thinking 3 rows of 6 each
3] Optics : Is 90 degrees good for planted tanks with regards to spread and penetration ?
4] Should the fixture be about the same or quite a bit smaller than the tank size ? Considering the spread with the optics and such that all corners of the tank should be lit and the highest that the fixture can be above the surface is 10inches.