types of halide lights?

[vdhillon]

hi,
i've seen that there are so many differnt types of halide lights....some big, some small, some one ended and so on. i'm trying to get into this more...but i need some help finding out whats a good halide for me.
What are the Kelvin ratings...is that more a color or power?
Can anyone tell me if these are good and if they would work?

http://cgi.ebay.com/ws/eBayISAPI.dll...ory=42883&rd=1

also there are the ballast..i hear electric is better, but why?

all this is for a 72 gallon i want to set up. i'll be taking apart a 30gallon which has pc lighting and adding that to the 72 along with the halides.

thanks

[inwall75]

You don't want these unless you like the color yellow instead of clear. These are clearly for people who grow MaryJane indoors or hydroponics as opposed to reef tanks. These max out at 4200k.

All you need to grow corals is 6500k. They will grow very fast with that but they will all be brown. At the other end of the spectrum is 20k lamps. Slow growth due to the low intensity (even at 400w) but great color. In between, you have 10k (with or without actinics), 12k, 14k, or 6500 supplemented with Actinics.

K=Kelvin=Spectrum (Remember ROYGBIV from Earth Science?)
W=Watts=Intensity taking into account that higher K = lower intensity. (That's why there is no such thing as a 175w 20k bulb...the extra wattage is necessary to increase the intensity or PAR).

Electronic ballasts use less electricity than tar and magnet ballasts and don't build up a lot of heat.

As a general rule, double-ended fixtures put out more PAR. Depending on what you are growing and the depth of your tank, this may or may not be important.

Play with this link for a bit and it will make more sense. http://metricksystem.com/chris/250wcolour/

[vdhillon]

inwall75,
thanks alot that helped alot...it makes almost complete sense now...and that website was great help seeing the differnt colors.
one more question though...when a ballast says its rated for M57 or M58 or H37 MERCURY VAPOR what does that mean?
thanks

[Birdlady]

Alright, I like that comparison site!

In theory, could you use a 6500K bulb with actinics and get the best of both worlds? Growth and Color? I see the 6500K bulbs are smoking in the PAR department. Is there a certain percentage of watts you need to reach that point, if possible?

I run a 175 10K MH with 96W X 2 VHO Actinics (the full length of the tank). I am considering an upgrade on the MH to a 250....

[inwall75]

Yes you can. I know of a lot of people who successfully kept awesome tanks in this manner.

However, this is where you need to know the critters in your tank. There is a point of diminishing returns where all you MIGHT be doing is wasting electricity as opposed to encouraging growth. If you are keeping deepwater specimens and you watch them close up their polyps halfway during the day, then moving up in wattage will just make them close their polyps sooner in the day. On the other hand, if you keep mostly softies and LPS that live in lagoonal areas or SPS that live on the shallower reef crests, then more intensity will typically cause quicker growth. Luckily, most corals are able to adapt to our tanks over time. Have you ever purchased a great looking SPS, watched it turn brown in your tank, and then start to color back up? That's what it's doing, it's adapting (and possibly grabbing a different type of zooxanthellae that helps it in your tank).

In the context of this article, the term photoadaptation is used to describe the ability of the organism to alter its structure and function in response to the characteristics of the light in its environment. When a coral from the wild or another tank environment is placed in a reef aquarium it has to photoadapt to the various aspects of light — the intensity, spectral distribution and direction of light. The basic adaptation mechanisms employed are various combinations of change in the chlorophyll content per unit surface area, change in the number and size of zooxanthellae, changes in coral morphology to increase the surface area available for light capture, and changes in respiration rate. More recent research is indicating that the corals may, in fact, harbor different types of zooxanthellae and the corals may be able to change the mix of the zooxanthellae as a photo adaptation response.

At the compensation point, the rate of photosynthesis equals the rate of respiration. As the light levels are increased beyond the compensation point, initially the rate of photosynthesis increases almost linearly with the increase in irradiance, but eventually the rate of photosynthesis begins to level off. The range of irradiance values where photosynthesis does not vary with irradiance is called light saturation. The light intensity required for saturation varies from species to species and also depends on other parameters, such as temperature and CO2 concentration.
The plot of photosynthesis as a function of irradiance is called a photosynthesis-irradiance (P-I) curve. These curves are of interest in understanding how an individual coral fares under a given light source. The P-I curves of photosynthesis are different for different corals living in shallow, well-illuminated areas when compared to corals living in shaded or deeper areas. The corals adapted to low illumination have steeper slopes in the initial part of their P-I curves, thus indicating that these corals can reach saturation sooner at lower light levels. This increase is primarily due to an increase in the number of zooxanthellae (Sorokin 1993). In general, these curves are hard to obtain. What is interesting is that photosynthesis may actually be inhibited at high irradiance levels, although photoinhibition has not been reported for corals in the natural environment.

http://www.personal.psu.edu/faculty/...osynthesis.htm

Too much light by Dana Riddle If you want to understand the symbiosis between Zoox and their host coral, this is a good link.

Coral Reef Zonation If you want to know where a lot of different corals come from, this is a good link.

Basically, Intensity allows zoox to function more efficiently, so less of them are required to "get the job done". With enough intensity, zoox are operating at their peak. If the coral doesn't need that much Carbon (sugars) or Oxygen, the coral will expel SOME of the zoox. Since the zoox is brown, once the coral expels the extras, the color of the coral will come back out.

The other consideration is obviously keeping our tanks too nutrient rich for the specimen. It's hard to have too many nutrients for softies. However, SPS live in Oligotrophic conditions. If you keep your tank too nutrient rich, you can offset the extra food going to the zoox but increasing photoperiod, intensity, etc. but it's a losing game. Eventually, if your tank keeps getting dirtier and dirtier, no amount of light is going to overcome the fact that you are giving the zoox too much food. Eventually one of two things willl happen...you'll have a tank filled with brown corals or the SPS will bleach.

[Birdlady]

OK Curt...Thanks....looks like I have a bit of reading to do!