Tank upgrade, do I need more lighting from HQI?

[wetWolger]

I am currently in the process of planning out my tank upgrade. I am going from my 4ft 120gal to a 6ft tank.

Currently my 4ft tank has 2x250watt MH mogul lights.

For my new tank I have purchased so far 2x400watt double ended HQI.

My original plan was that with the higher wattage, as well as being HQI (I have been told HQI produces more par? not sure if that is true) that I would be able to hang them higher over the tank to get the light to span the 6ft length of the tank.

I don't believe I need more intense light than I currently have. But I will be changing from a 24in deep tank to a 30in deep tank. I do currently keep SPS just fine, and I one day want a clam as well.

So my question is, would the 2x400watt HQI, raised high enough to spread the light over the 6ft tank, be enough light? Would this at least match how much light I am currently giving the 120gal aquarium? Or should I plan on getting a 3rd light? It's not so much the cost of the light that makes me reluctant, as just trying to conserve electricity if possible (again, not cost, just green). Thanks for any input on the matter, and feel free to ask my any questions for details I left out.

 

[sassafrass]

The optimum solution I have found is to use one 400 watt and mount it low on a lightrail , it uses less power reduces heat transfer and as the light traverses the length of the tank it always looks a little different . If you have any questions feel free to ask , I have done this several times with success.
Lee

 

[Jflip2002]

You could get away with (2) 400w MH over your tank, but it wouldnt work with a fixture. Youd need a nicer reflector like a lumenarc or lumenmax, for better spread. Ive got one 400w MH covering my 36" tank, with no dark spots. So I think youd be safe.

 

[wetWolger]

<a href=showthread.php?s=&postid=14772322#post14772322 target=_blank>Originally posted</a> by Jflip2002
You could get away with (2) 400w MH over your tank, but it wouldnt work with a fixture. Youd need a nicer reflector like a lumenarc or lumenmax, for better spread. Ive got one 400w MH covering my 36" tank, with no dark spots. So I think youd be safe.

That was actually the plan. I got two Luminarc 3 20” reflectors for it. Hoping they would be good enough to spread the small intense light over the distance without me having to raise the fixtures too high.

From the sounds of it, it is at least worth a try.

The light mover was a great idea, I wonder how slow can they move and still be efficient at providing good light for the entire tank? Might be cool to watch it, go away for some hours, come back and the light is on the other half of the tank. Could give it a unique flare. But I don't think I would want it obvious that the lights are moving if you only look at it for 1 or 2min.

 

[Jflip2002]

I have a 36x36x20 tank, with a 400w MH under a lumenarc III.. Its only about 6" off the water right now, and there arent any dark spots (besides caves). I think the two will work if you put them 6-8" above the water, depending on what youre keeping, and how tall your tank is.

 

[wetWolger]

Wow, that is really good to hear. I was imagining further than 6in to accomplish a 36in spread, was expecting like 12. So now I am excited :3