Hello,
I am starting a DIY Led project. I have purchased a DIY kit.

I know that I don't need 24 leds for my aquarium, which by the way is a 20 gal with a 10 gal sump. I chose 12 3w white 10000k leds and 12 3w Royal Blue 452-455nm leds. Will use the extra leds i don't use for another project.

My plans for the aquarium are a couple of fish, and i would like pulsing xenia, polyps, and soft corals.

If my math is correct, i need about 18 leds, using the wpg rule along with lumens and par rating. I originally thought to use 9 white and 9 blue with 60 degree optics, but i looked at some led hoods and such, and most of them use a 2:1 ratio. I guess it just really matters on the colors you are looking for. What do you suggest, do i have enought leds for my tank, too many, and what ratio would you use. Any help would be appreciated.

Thanks.

18 3W LEDs is a lot of light, especially for the animals you want to keep.

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how many would you suggest? and ratios please.

You don't really do ratios with LEDs. You can't use techniques that you would with fluorescents when trying to figure out how many you need. With the 3W LEDs and the proper driver, you shouldn't need more than 6-7 if you're just going to be doing low-light corals.

*edit* Forgot to give you the formula for figuring out how many LEDs you want. You want roughly 1 3W Cree per 15 square inches of aquarium surface area, with optics for deeper tanks and more LEDs if you're doing light-intensive corals like SPS. The mix of blue:white is fairly subjective, but a 1:1 is common. I've seen people do 2:1 blue:white, and 1:2 as well; it's more a matter of taste. Use a dimmable system and you can adjust the colors to your tastes.

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