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Originally Posted by **bohmert** Just looked. Cant find 48inch. It is 18 deep |

At 18" deep, you could essentially get away with a four bulb T5HO fixture. You can probably get one for about $200. I like

but these do not have lunar lights. Brands such as

and

make units with Lunars, but you will pay for it. I have never used either of the latter two brands, but reviews seem decent on Amazon...

In a 75 gallon, 216 watts gives you roughly 3 watts per gallon. I have never been a fan of "watts per gallon" since it is all about light penetration and different tanks have different heights, so watts per gallon doesn't really work.

I always used a formula that comes to a penetrating wattage of at least a 1/4 watt per depth inch. I take the wattage and divide it by tank length (216w/48"=4.5). I take that result and divide it by the depth (4.5watts per length inch/18"=.25). This comes to a 1/4 watt per depth inch.

For illustration purposes, a 72", 3 x 250w HQI has 750 watts of light over a 150 gallon tall (72" L x 18" W x 28" D) would end up with .372 (about 3/8) of a watt per depth inch (750/720=10.4/28=.372). So in my estimation, getting that wattage to somewhere between .25 and .4 for a reef tank will help the animals thrive in this closed enviroment.

Rememeber too that different lights have different wattage power. HQI (metal halide) penetrate much better than T5HO and LED. Good LED's can penetrate better than Flourescents. I have owned every kind of light fixture and prefer LED the most. I hate replacing bulbs every six months...