really confused about lighting

[proy]

This is a great forum, I've read almost all the lighting questions and I'm still very confused about lighting. I'm looking at getting a 108 gallon 60x18x24 tank, and I would like to eventually be able to support all sorts of coral. I can either make or buy a lighting system.
Recommendations please

 

[marine qa]

I am by no means a lighting guru, but to support "all sorts of coral" you are going to have to be very well equipped indeed. This means you are going to need conservatively 4-6 watts per gallon (math 108x6=648 watts) Here are my suggestions:
2 250watt Metal Hallides, supplemented with 2+ 60inch VHO Actinic (blue) flos.
OR possibly 3 170watt Metal Hallides, again supplemented with Actinic VHO flos.
You will receive other suggestions, but dont listed to them. It just so happens that I have 2 250watt metal hallides for sale, and I also have 3 170watts MHs for sale. They may cost more than you see other places, but believe me their worth it.
Just kidding about the MH for sale and not listening to other's part.

 

[reefkeeper1]

what would you want for your lights? the 250 and the 3 175? what type are they and are they electronic?

 

[amir]

I like to buy 2 do you know a good plce to buy ?????

 

[option720]

Okay, let’s get back on subject here.
You say you want to be able to keep all sorts of corals, so I’m going to assume you will want some SPS, LPS and some Softies. The first thing you need to understand is that corals need a certain amount of light Intensity in order to survive. There is a popular myth in this hobby that based on how many “watts per gallon” you have will determine what corals you can keep, I’m telling you right now to save you time and money, the theory is crap. Check this out:
Following this "rule of thumb", 100 watts over a five-gallon tank (20w/g) appears much better than that same 100 watts over a ten-gallon tank (10w/g), but the intensity is lacking in both cases. One hundred watts is still one hundred watts, no matter how you slice it. Intensity is the key, the more the better. If a coral, for example, requires 15,000 lux to saturate (survive), it needs to get that amount of light regardless of tank size. So, if a 175 watt metal halide puts out 17,500 lux at the water surface and 8,000 lux ten inches down, it’s enough light for the coral at the surface but not at the bottom.
You see the amount of light you have means little, the intensity of light you have means everything. Please read this article for some more info on lighting in a reef.
<a href="http://www.animalnetwork.com/fish2/aqfm/1999/july/features/2/default.asp" target="_blank">http://www.animalnetwork.com/fish2/aqfm/1999/july/features/2/default.asp</a>

 

[10k]

Finally someone understands the art af reef lighting! Bravo!!

 

[marine qa]

I still stick by my suggestion, and I think many will agree with it. Intensity is key, and that is why I suggest MHs (to provide adequate intensity) in combination w/VHO Actinics (that make your fish/corals look cool under blue light). The wattage per gallon rule is not a perfect formula, but it does provide a good place to start.
Option720,
The article you suggested was informative and I believe it supports my suggestion that high wattage is important to provide adequate reef lighting. The author stated:
"By 8:00 a.m. light intensity [found in a natural reef] exceeded the intensity found over a tank lighted by 400-watt metal halide bulbs."
The author goes on to say:
"As the sun rises, light intensity increases more or less linearly until noontime, where it reaches over 2000 µE/m2/sec on a day without clouds (see Figure 1). This level of intensity is virtually impossible to recreate in a captive system with lighting commonly available to the hobby. A 400-watt metal halide bulb generates 2000 µE/m2/sec within a few inches of the envelope."
In short, the author does not discuss MH bulbs with less wattage than 400watts because they would be even less adequate in imitating the intensity of a natural reef's lighting than a 400watt MH would be. Wattage is what carries light intenstiy through watter.
Using your example: "if a 175 watt metal halide puts out 17,500 lux at the water surface and 8,000 lux ten inches down, it is enough light for the coral at the surface but not at the bottom." I assert that the reason the 175w's intensity is inadequate for the bottow of the tank is because the wattage is to low. If you used a 250 or 400watt MH with 17,500 lux (if available) instead of a 175watt you would have enough lighting intensity for corals at the bottom of the tank.
I have no doubt you understand the principles of reef lighting, and because of this it would benefit the board to hear your lighting suggestion for proy if it differs from mine. Furthermore, I apologize if I misunderstood your point, and please correct me if this is the case.

 

[option720]

Marine QA
No worries, there are no hard feeling here. I just want the new person who comes to this board not to read a post about watts per gallon and think they can put sixty 20 watt Normal Output bulbs over a 200 gallon tank and keep any coral they want because they have 6 watts of light per gallon. I think you and I are on the same page here, and it basically just comes down to knowledge about the life you want to keep in your tank. If you want and Acropora that will only survive under a 400 watt 6500k bulb and it must be placed in the top five inches of the water column directly under the bulb, then that’s what it going to take to keep that coral.
In response to the comment:&#8221; I have no doubt you understand the principles of reef lighting, and because of this it would benefit the board to hear your lighting suggestion for proy if it differs from mine.&#8221; I thank you for the compliment but just as you I make no claim to be an expert. My suggestion to Proy, is determine what corals and livestock you want to keep in your tank first, and then buy your lighting based on the need of those animal. There is no exact formula of combination of lighting that is guaranteed to work. Many people claim you can only keep clams Metal Halide bulbs while other harvest clams under Power Compacts. I actually like the suggestion the you gave Proy. I think that two 250 MH with the VHO actinics would be a great setup that will allow for a variety of corals to be kept at various depths though out the tank.
Now as for what color bulbs to choose, I’ll leave that for someone else to start a flame war over