10,000K or 20,000K MH?

[IndyReefMan]

It's about time to replace my MH bulbs. On my 72 gal bowfront, I'm currently running 130 watt 10,000K PC, 130 watt actinic PC, and 2 x 150 watt 20,000K MH. I really like the blue look of the 20,000K MH but am wondering if my SPS might do better with warmer color temp bulbs for my MH. I currently have a few softies, a few SPS, and a lot of LPS. I would like to start stocking more SPS. I recently read that since SPS are primarily shallow water corals, they prefer warmer color temps (eg- 6,500K). I'm afraid that warm a color temp might fuel more algae growth, plus I'm not sure that I would like that yellow look. Should I switch to 6,500K? Maybe 10,000K on the MH, or 14,000K would be better... decisions, decisions. If I do change to a different color temp on my MH, I'll have to do it very carefully so I don't shock the corals. I'd welcome some opinions on this.

 

[DragonForce]

14k would be what I would go for, but I am new at this hobby. I wish I went for a 14k instead of 10k

 

[HoopsGuru]

I would not mix SPS with a bunch of LPS. Even if you space them out, SPS will grow pretty quickly under the right conditions and will be in trouble with the sweepers and general aggression of the LPS. Garden aquaria rarely work long term.

If you are willing to choose between the two and go with SPS, it would really come down to preference, although if you plan on keeping the highest light species I would consider upgrading to 250w MH even though you have the PC's.

 

[IndyReefMan]

Any other opinions?

 

[revhtree]

If you like the blue, but want a warmer color, I would go with a 14k or 15k bulb. On the other hand if you have plenty of actinic suppliment, then go with a 10k. IMO you need to get what will satisfy you and the look your going for.

 

[IndyReefMan]

If you like the blue, but want a warmer color, I would go with a 14k or 15k bulb. On the other hand if you have plenty of actinic suppliment, then go with a 10k. IMO you need to get what will satisfy you and the look your going for.

How about for coral growth and general health... is there much difference between the 10,000K and 14,000K?

 

[Salttanker]

I like the color of my 14K's. I use a pc actinic to also supplement the blue with, but you could run the 14's without anything else and it would look good.

I have heard the 10K is better for growth, but I'm not positive.

Mike

 

[steve-s]

I would look at it slightly different. Light color for your personally veiwing is not as "important" so to speak as the needs of the corals. In terms of specrum, the best is really in the 6500-6700 range. The higher you step it up, the slower the corals tend to grow and less colorful overall. That said, the highest I would go is 10,000k. It may still have some yellow but not as much as the 6500 and still offer what the corals needs. As far as color ascetics for you, simpley add actinic supplimentation.

There are alot of good articles here...
http://www.advancedaquarist.com/index/FA.shtml

I would also pay special attention to the reflector as well. That can often make or break the effectiveness of the chosen lighting scheme.

Cheers
Steve

 

[DragonForce]

Not to hijack the thread, but steve, do you think 20 watts of actinic supplementing would give me a nice look in addition to my 175 MH 10k in a 37 gal as well as be sufficient for corals?

 

[hcuellart]

The best growth and overall looks will be with a 10,000K bulb supplemented by some actinics.

 

[revhtree]

IMHO...Humble opinion.....

The reason I have a tank is for my enjoyment. I believe if I am not doing anything to harm the inhabitants of my tank, then I am going to get what looks good to me.
14k or 15k is not going to kill your corals. They will grow slower maybe, than with the 10k. Then again if my water conditions are better than yours with the 6500k, I am going to get better growth with the 15k anyway...

Now I know this didnt address your question exactly, but to me it boils down to what I am going to be happy with. You had mentioned you wasnt sure you would like that yellow color.....You need to be happy with what it looks like. Whats the point in growing faster corals if everytime you look at the tank you think, "man that yellow sure is ugly."

I also deeply understand where Steve is coming from. It is a choice that you must make and be able to live with. For Gosh sake man, it's your reef were talking about here!!!

 

[steve-s]

Not to hijack the thread, but steve, do you think 20 watts of actinic supplementing would give me a nice look in addition to my 175 MH 10k in a 37 gal as well as be sufficient for corals?

I wouldn't use an NO type bulb personally. You will end up with the same/similar spectrum shifts as the kelvin rated bulbs. Go with the appropriate VHO, PC true actinic or T5 bulb suitable for your tank length. You'll get much better "umf" as the NO will have a tough time competing with the intensity of the MH. Don't worry about the output of a higher wattage actinic in relation to the MH usage, it's impact overall will be minimal. Just be sure the tank gets photo acclimated if adjusting the intensity upwards.

Cheers
Steve

 

[IndyReefMan]

Thank-you very much for all of your valuable opinions. I really like the blue look but want to take good care of my reef. I will go to several different LFS and examine what their tanks look like under different color MH bulbs... I guess that I'll need to study them first hand. Coral growth seems very slow with my present 20,000K MH. If I go with the 10,000K and it is too yellow, I can always replace my 10,000K PC with another set of actinics. One more question... if I do change to 10,000K or 14,000K MH, what type oy photo acclimation procedures should I use (if any)? The "screen method"? or is photo acclimation even necessary when switching to a lower color temp, yet same wattage bulb?

 

[Hara]

I sometimes wonder if slower coral growth is really such a bad thing. ...If the corals are healthy and "big enough" for you, what is wrong with slowing the growth and having a tank you like the appearance of?

 

[IndyReefMan]

I sometimes wonder if slower coral growth is really such a bad thing. ...If the corals are healthy and "big enough" for you, what is wrong with slowing the growth and having a tank you like the appearance of?

Very good point. After having my reef set-up for just over a year now, it still looks like a mountain of live rock with corals just sitting on display. In other words, it doesn't look very natural. I want a little more growth so that the corals will start to "fill-in" and look like a more natural reef. I picked up a book called "ultimate marine aquariums"-- a fantastic book for those of you not familiar with it. Those folks have gotten their reefs to look very natural. I just haven't had the growth to be able to do that. Then again, it's only been set-up for a year. Maybe I'm just being impatient.

 

[MT79]

I sometimes wonder if slower coral growth is really such a bad thing. ... what is wrong with slowing the growth and having a tank you like the appearance of?

I see what your saying, but it is always nice to have a frag to exchange for a credit at the LFS. I would love for my tank to be partially self sufficient cost wise...maybe some day lol.

 

[lando]

Interesting thread. I just order a MH fixture with 2x175watt 20K bulbs and 2x96watt Actinic CF. I am very worried this will be too blue for my tastes. Appearance aside, is there anything detrimental about using 20K bulbs?

 

[Hara]

I loved the look when I had all three 250 watt bulbs being 20k.

 

[greenmaji]

When Steve said 6500-6700K I was thinking planted tank and was a bit taken back with it.. I personly think that 6500K looks a little blue (I actually wouldnt mind and might like the look).. I still thought that the coarls needed the 03 for growth or heath sake. If not, is it just for the viewing the floresence? The HQI 6500K Iwasaki MH bulb seems to be a great performer from the posts (to articles) Ive seen here, is it the color of it that keeps people from using it more often (they dont make a 175W version of the Iwasaki from what I can tell but if it performs so well PAR wise couldn't you go with a 150W instead)?

 

[steve-s]

Appearance aside, is there anything detrimental about using 20K bulbs?

Not really no. Other than reduced coral growth, the health of the coral is generally not impacted although coral coloration may vary. It is extremely important that when increasing kelvin as with intensity the corals are allowed to adjust gradually over time. The "screen" method being the most effective. It allows the photoperiod to remain the same but the corals are given the opportunity to adjust to the changes otherwise gradually without significant impact. Kelvin increases can be just as damaging as light intesity increases. Bluer kelvins are not the same as actinic in that regard.

I still thought that the coarls needed the 03 for growth or heath sake. If not, is it just for the viewing the floresence?

Actinic lighting is purely ascetic, there is little to no benefit to photosynthetic life other than added light intensity. Tanks without 03 supplimentation are no worse or better off without it. It's merely a matter of preference. Reef hobbyist tend to augment the light to their taste over that of the corals though in terms of MH K's.

The HQI 6500K Iwasaki MH bulb seems to be a great performer from the posts (to articles) Ive seen here, is it the color of it that keeps people from using it more often (they dont make a 175W version of the Iwasaki from what I can tell but if it performs so well PAR wise couldn't you go with a 150W instead)?

More commonly it's a visual preference that keeps people from using the lower kelvin bulbs. If using strictly MH without 03 supps, the light output is very yellow and can make a tank look dank & dingey. This is where people often opt for higher K's to offset the yellow color. It terms of the corals preference, the 6500 will provide the best environment for coral growth and often color. It's easy enough to add the necessary 03 supps to alter the "visual" perspective so the hobbyist can enjoy it as well. Cost is usually the only limiting factor.

Cheers
Steve