lighting question

[ou812pezz]

I have a 48" Aqualight Pro, 2x 150W HQI (10,000K) + 2x 96W Actinic + 3 Blue Moonlight LEDs over a 100 gal tank. What kind of color difference(in the corals) would there be (if visibly any) during the daylight hours between a 10,000k HQI bulb and a 20,000K HQI Bulb? I ask because I have some green staghorns that are now tan. My purple monti caps are dark brown in color. All my other sps look fine.

[gjuarez]

Sps corals normally brown out or tan when there is an excess of nutrients. What do your phosphates and nitrates read? 20k lights sure bring out more color in corals, but they shouldnt be tan or brown under 10k.

[GaryP]

There are two seperate issues when it comes to color on bulbs.

1. Reflected light. Obviously, different colors light reflected from the tank is going to look different to the observer. A 20K is bluer then a 10K. Unfortunately, a 20K also puts out half as much light as a 10K and your growth is going to slow considerably as well.

2. Spectrum and coral pigment production. Some 10K bulbs put out more purple light (420 nm) then a 20K. 20K mainly put out more blue light (460 nm). The same can apply to the "actinic" bulbs in your fixture. True actinic is 420 nm while some are bulbs sold as actinic are really 460 nm blue bulbs. 420 nm is thought to be the wavelength that is most responsible for pigment production in corals. It is very close to UV light (<400 nm) and basically tricks the corals into thinking they are being sunburned. Many SPS corals respond to this light by producing the blue and purple pigments that we are looking for.

Just to give you an example, I gave Todd a rather boring brown robusta frag a few weeks ago. Under his intense lights it colored to a very pretty blue color.

[ou812pezz]

Phosphates and nitrates are 0. The only thing off is my calcium level. Its in the 500s(I haven't dosed a thing in 5 months) and my alk is 2.0. I'm in the process of raising my Alk( adding small dose of baking soda each day). Everything in the tank is doing fine and growing, It's just those two sps corals aren't showing their true coloration.

[hobogato]

give em time, i have some sps that were brown for 6 months before they started to color up. i have one that is brown that has been in my tank almost a year - it is just starting to color on the edge of the encrusting part and on the tips.

[Andrew]

The CF actinic bulbs lose intensity very fast IME. I'd replace them every six months, and use 420nm actinics, not the "dual actinic" that is sold with the fixture.

Other than that, I'd test the water as suggested earlier, and give the corals a little time before you decide to switch MH bulbs.
HTH
Andrew

[Andrew]

oh, just read that you tested.

[ou812pezz]

Thanks guys, I'll wait.

[ou812pezz]

Another question comes to mind. If a coral goes from a tank with much more light than the tank it now resides in, does that make a difference in coloration?

[hobogato]

yep, and the converse is true as well. not just more or less lighting, but nutrient levels and color of light, especially how much actinic seems to make a difference. many of my corals changed coloration when i switched from XM 15k bulbs to CV 14k.

[gjuarez]

Changing the color could have a negative or a positive impact. If the coral is not used to being blasted by high amounts of light it could bleach a little, but there is also a possibility that it could get better coloration. Like mentioned before, the amount of light is not the important thing when it comes to coloration. You can put a 400w 6.5k Iwasaki bulb and it will grow like crazy because they are super intense, but it will do hardly anything for the color. Gary gave us an example of a frag he gave to Texas Todd. Todd has an awesome lighting setup and he is using a combination of different bulbs, some of which include the reeflux bulbs. Reeflux bulbs peak at around 470nm and thats why it reflects nice colors of his corals. In addition, if I am not mistaken, Todd also has VHO actinic supplumentation that provides the 420nm that Gary was talking. 420nm not only reflects nicely of the corals but it also helps create the pigmentation in the zooxanthellae algaes. What type of 10k bulbs are you using?

[ou812pezz]

Coralife HQI Double Ended Metal Halides and Coralife Compact Fluorescent actinics. I can say that corals look bright during the actinic cycles(dawn and dusk) but are even brighter under the blue moon light. I think I should be patient for now. thanks everyone.

[gjuarez]

Yeah be patient, I have a couple of corals in my tank that have the most amazing color and then I have one frag that just browned out for no particular reason. Sometimes I guess it just happens. I am sure they will get their colors back in no time.

[GaryP]

I've had corals bleach out and I almost lost some when I went from an old higher K, lower PAR value bulb (Blueline 14K) to a lower K, higher PAR value bulb (XM 10K). My birdsnest was almost gone as a result. Sudden increases in light, even from replacing with new bulbs can have an impact. I noticed that Sanjay rotates replacement of his bulbs in his system. Of course he has something like 4 bulbs on his tank and replaces one every 6 months. But this practice would seem to even out the average light in the tank rather then getting a sudden increase every time you replace bulbs.

I learned my lesson and whenever I replace bulbs I cut back the timers and slowly increase the time they are turned on to help minimize the light shock the corals get. Other impacts can occur as well. More light = more growth = more demand for calcium and alkalinity. I watch my levels more closely after a bulb change to make sure my dosing keeps up with demand.