Metal Halide Question??

[mrinelfrlz]

ok right now i have x2 150 watt MHs that are @ 10000k color temp
now i know these are fine with my 75 gallon because i also have with it x2 44 watt blue actinics so its more then enough wattage
but will it help my coral and inhabitants grow better and give the tank a better effect if i went with either 14000k or up to 20000k
color temp. metal halides?

thanks

 

[tperk9784]

14k and 20k bulbs will have less PAR than the 10K bulbs you will get more of a blue color but less growth all around.

 

[aztec reef]

It wouldn't make a difference in growth, Is up to your preferance. do you want a little more blue in your lights? if you get enuf blue from your actinics then i would just keep it as is.

 

[stanlalee]

Originally Posted by Aztec Reef
It wouldn't make a difference in growth.
going from a 10k to a 14k usually does make a difference in growth all things being equal. there are some exceptions (a few really good 14k bulbs and a few bad 10k brands). 20k will most definately slow down growth over 10k bulbs.

 

[aztec reef]

So you're saying that if you have 14k, corals would grow less than if you have 10k. If so how much difference are we talking about in centimeters?

 

[johnny84]

in my travels I noticed that my yellow fiji leather did better under the 20k lights, everything else I have is doing better now that I switched to the 10k bulbs, everything but my yello fiji leather.

 

[aztec reef]

yeah i also think it depends on type of corals you have...like if you have a SPS tank dominated then it will most likely make a difference going 10-14k. but i don't think it will be noticible. btw we're taking about acouple 150watters so i don't think there would be a difference..

 

[tperk9784]

PAR is the measurement of usable light given off by a bulb. The better the PAR the better potential growth in your corals. 20k and 14k bulbs historically give off less PAR than 10 K bulbs. Less PAR equals Less Potential growth.
If you want a good mix of growth and color I would go with a 14k bulb. Hamilton for less blue, Pheonix for more blue. In the end it's all about how you want the tank to look and what you are trying to achieve.

 

[mrinelfrlz]

thanks for all the feedback everyone

i sounds like that 14k might be the way to go not alot of blue but a little
because on my actinics the MHs always drown them out
but i do want good growth still
thanks again

 

[stanlalee]

Originally Posted by Aztec Reef
So you're saying that if you have 14k, corals would grow less than if you have 10k. If so how much difference are we talking about in centimeters?

well lets put it this way. XM brand single ended 250w bulbs on the same magnetic ballast have the following PPFD readings (simular PAR. PAR percentage difference will be simular or the same):
10K 137
15k 55
20k 73
and EVC 250w bulbs
10k 96
14k 55
20k 45
So you are looking at about half the PAR or worse in many cases jumping from a 10k to a 14k/20k bulb.
For reference: 175w 10k XM bulb (also magnetic ballast) PPFD 62. the 175w 10k bulb puts out more PAR than the 250w 15k and in the same realm as the 20k bulb. I cant tell you how many millimeters difference in growth that is but the performance difference speaks for itself. We are not talking about a slight or little bit but huge performance differences. Softies and LPS might not care but with SPS you will certainly see a difference with twice the PAR. Honestly a few better 14k bulbs perform just as well or close to many 10k bulbs but its the exception not the rule (just like the XM 20k outperforming the 15k is the exception. with most brands those two would be reversed).