# DIY LED Question



## caker_chris (Apr 22, 2010)

I am about to order some led's for a DIY lighting project for my tank. I was just wondering how many I would need for a SPS 75 Gallon tank that is 48x18x21?

I was thinking of going with either:

16 Blue and 14 White

or

36 Blue and 34 White

What do you guys and gals think?


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## Kooka (Feb 8, 2011)

There are a number of things to consider when doing a DIY lighting setup. Will your lights be dimmable? What kind of LED's and drivers will you be using? Assuming you'll be going with Crees, I would do a 2:1 or even a 3:1 ratio of Royal Blues to Neutral/Cool Whites if the fixture will be non-dimmable. If you plan on using potentiometers or a controller to dim each strand of LEDs seperately, you can go with a 1:1 ratio of each color. 

The cool white LEDs are very powerful, and tend to really wash out the warmer colors in your reef. On my tank, I usually run the blues at twice the amount of current than the whites and I find that combination brings out the nicest colors from the corals. I've read on some other forums that people now are recommending to reduce the amount of cool white used, and instead supplement them with red, cyan and violet leds to bring out more of the reds, pinks and purples in the tank. You can also try the neutral white leds since they produce a warmer light. I think its a matter of personal preference, and even if you go with the tried and true standard of cool whites and royal blues, you'll find them to be much better than flourescents.


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## caker_chris (Apr 22, 2010)

ok sorry a wanted to know more if the 30 3W leds would be enough light for a 75 gallon SPS or if I should go with more?

If I should go with more how much would you think would be good?

They are cree and will be dimmable.


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## liz (Jan 16, 2008)

If they are 3 watt crees I would go with 48 - two heat sinks with 24 on each. Also depends on what you plan on keeping? softies or SPS?
Check out Rapidled.com they sell the 48 kits.


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## altcharacter (Jan 10, 2011)

I'm with Liz, and he did say sps in the first post. More is always better of course but if you divide up your heat sinks it will be a little more cost effective and eventually something will happen to your lights (ask damsel_den) and if you sink one in the water it's better than all 2 or 3.

With a tank your size you'll need optics so your light can reach the bottom of the tank. Using optics means that you'll need to either mix up the optics so the top can get light also or putting in more LED's. 

If you space your LED's 4 inches apart in a pattern of 6x4 your LED's would spread over a space 24x16 and with 2 heat sinks spaced apart you could effectively cover an area of 55" or so total. Although you would have to buy 2 heat sinks that are 24" and that might be a bit expensive. Three arrays of 18 LED's each might work better but thats just a opinion.

i'd go with 2 royal blue to 1 white. The whites are definitely bright.
Good luck!


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## caker_chris (Apr 22, 2010)

ok thanks for the help


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## Kooka (Feb 8, 2011)

Whoops, forgot to answer that question. Liz is right, 48 would be perfect for a 75 gallon. Just take into account what Alt and I mentioned, 2 blues for every 1 white LED will help with your color balance. I would even try adding in a couple of cyans, reds and even violets to bring out the warmer colors as well.

Good Luck on your light!


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