led lighting question

soooo i have a led light system with dimmers its 10 white cree and 10 royal blue cree led's.
my question is i plan on suspending it from the ceiling but i want to suspended it in a way so its out of sight. and in order to do that the lighting will be 20 inches from the top of the tank. it will be over either a 55g or a 40g breeder with the breeder it will be 24 inches from the top of the tank i will have 90 degrees lenses on them, you think the light would have the penetration to get to the bottom

 

IMO get a 36 led kit from Rapid or Stevesleds and use a 1:2 ratio of NW:RB and add some DR, CB, TV, and if you can, some cyan

 

i plan on adding those in the future but i just wanted to know if it would work for now till i can get those in. i planed on in the future adding. 5 more blue, 2 cyan 2 violets, and 2 cyan/green. here is the next question, should i put all of those on the same dimmer or have a different ones for the ones i plan on adding

 

fyi this is a fowlr right now, it will later be turned into a frag tank/reef tank

 

Well with 36 you don't have to upgrade to a better spectrum/larger number of leds.
Change the CW to NW and make it a 1:2 ratio with the RB

 

i already have the DIY system of 10 white 10 blue, my main question is how high is to high when you start to suspend over a tank. i plan on adding 2 DR 2 cyan 2 UV and 6 more RB all with 90 degree optics on them. is 24 inches off the top of the tank to high?

 

You can calculate coverage area as TAN(lens angle /2) * distance * 2. Technically, the light won't be consistent over the entire area, and will drop off as you move from the center. so, you may want to reduce that, some people use 75% of the area, so, that would be TAN(lens angle /2) * distance * 1.5.

So, TAN(90/2) * 24 * 1.5 gives you a 36" circle. That is per LED though. So, then you need to add the spacing of the LEDs. So, if say, the fixture is 24" long, by 12" wide, now you have 36"+24"=60" coverage on the length and 36"+12" = 48" on the width.

A standard 55g is 48"12.5 and a 40B is 36" x 18" So, either way, you'd be getting about as much light on the floor as in the tank... Usually, I plan an LED by optimizing coverage for 1/2 way down into the tank. So, if the tank is 18" tall, 1/2 is 9, so, I would calculate the optimal lens as 24"+9" = 33" for example.