Quote:
Originally Posted by gobytron
Do you really get the same penetration and par with something like a 6 bulb tek fixture (this is the fixture I would try to find if I did switch to t5) or something comparable?
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To answer the question very simply...ABSOLUTELY NOT.
This question has been debated to death. You will have the T5 diehards, and the MH diehards who will have differing opinions, and usually strong opinions at that. I used to be a diehard MH, then I switched to T5 and thought that was the cat's @$$, now I'm back to MH.
Depth penetration is a fairly straight forward answer even though you will get differing opinons which is kinda silly if you ask me, as there are numerous "case studies" that show T5 does not even come close to the depth penetration of MH
when compared fairly.
Now, when people are comparing MH to T5 for PAR they USUALLY don't compare fairly as it is difficult to do. First, you need 8x54w T5s to fairly compare to 2x[any watt] MH lamps or 4x54w to a single MH lamp. Otherwise you are not getting the same coverage of sq ft of usable light. Next, you have to compare the same Kelvin. You can't compare 10000K to 14000K and say that you have compared fairly because the higher Kelvin puts out less PAR in comparison to the same bulb in a lower Kelvin. Then you have issues like reflector quality. And the biggest variable?? What bulb/ballast combination? If you pick a poor bulb/ballast combination you may get 1/4 of the PAR out of that setup as you would if you ran a different bulb/ballast combination of the same wattage. You can also get more PAR out of a lower watt than a higher watt just by choosing different bulbs/ballasts.
SO...if you want to compare fairly, or you want a more accurate answer you need to ask something more like this:
Will I get higher PAR from 2x250w electronic ballasts with Giesemann 13,000K DE bulbs and LumenMax 3 reflectors or a 8x54w Tek T5 running 3 Fiji Purples and 5 AquaScience 15,000K??
The answer to that would be that you would get higher PAR from the MH set up in this particular case. I'm going to take an educated
guess and say you will get about 25-30% more PAR out of the MH at 24" depth. Although the PAR at the water's surface would probably be within 10-15% of eachother, with the MH still leading.
Another issue with lighting that many many people fail to consider is water clarity. There are many reasons for higher or lower water clarity, and generally people with less experience are less likely to have high water clarity. This HUGELY affects the amount of light penetration, and is not as easy to achieve as you may think. I'm not going to go into that any more though because that's a fairly large topic as well.
Quote:
Originally Posted by gobytron
I thought I would query this great forum for peoples experience with a tank of this depth and t5 vs mh for sps, clams and other high light loving organisms...
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Imo, there is no comparison in your case with the combination of significant depth (24") and the critters you are keeping. MH would be the ONLY option if I was in your place. Oh, and I am!! I am setting up a 24" deep tank, and am using 2x250w MH with supplemental T5 blues/actinics. I absolutely would not consider T5s for my tank, and I only keep LPS, a lower light clam, and a lower light anemone. Although I do plan to add a few SPS to the tank.