what spectrum should i use

sk8now2003 · #1 (**permalink**) 04-08-2008, 10:28 PM

i am setting up a 120 gallon lps,sps, and soft coral tank. i am thinking of running 3 250 watt metal halides? would you recommend this or is this over kill and what spectrum should i use?

ricosuave · #2 (**permalink**) 04-08-2008, 11:30 PM

For 2' deep 175w is good enough unless you have clams. I would say 250w is ample. Any deeper and you will definitely need 250w maybe even up to 400w if you have 30-36" deep.

sps and clams require more intense lighting probably at least 5500k to 10000k that will be mostly white. 12000k to 20000k will get progressively more blue.

Softies, especially mushrooms can tolerate, sometimes even prefer, lower lighting levels.

Before you purchase the lighting I would suggest that you search this site as there are numerous threads that i am sure will have the answers you are looking for.

These are just my opinions and you should wait to hear from more knowledgable people here before you make your final decisions.

Hope this helps.

sk8now2003 · #3 (**permalink**) 04-09-2008, 03:03 AM

would you say that 3 fixtures of either wattage would be sufficient or do i only need 1. i am thinking of keeping clams and sps. if i was going to get a 250 watt i would keep the mushrooms and soft corals under a ledge or figure out where the lighting is less intense. Thanks for your opinions, i appreciate them and please keep them coming.

ricosuave · #4 (**permalink**) 04-09-2008, 04:50 AM

I am just a novice by far, but what I have learned is that you need one light for about every two feet of tank. Your tank is 4x4 so you have roughly 4 spaces at 2x2. Maybe overkill, but i would probably go with 4 @ 250w. That way you could balance it out and everything would look even, not to mention of course that you would have plenty of light for sps and clams.

DaveK is very knowledgeable about lighting. Are you there Dave? Am I off course?

**DaveK** · #5 (**permalink**) 04-09-2008, 07:57 AM

Usually a 120 gal tank is either 4 feet long or 6 feet long, depending upon the width of the tank. Assuming it's a 6 foot long tank, three MH bulbs should be fine.

The usual factors apply. You'll get more light out of a 250w bulb, but also more heat. In larger tanks it's also possible to use different lighting in different places. For example, you could use one 250w bulb and keep all the SPS and clams under that. It's more a balancing act rather than a hard fast rule.

If you have an unusual tank, something like 4 feet by 4 feet, then you might want four bulbs running over the tank, such as ricosuave suggests. Then again, you might want something different.