Metal Halide PAR value

[Razor]

I recently found a comparison of 250W MH Mogul End bulbs, which is amazing and really outlines the different bulbs and ballasts.

While color is usually the most important characterisitc for us, or at least me, is the hghest PAR value the second most important or is too much of a PAR value actually bad for the tank.

What's the max PAR we should be looking for when buying a bulb, if any?

Thanks.

 

[Anonymous]

IIRC the amount of PAR is one factor on how fast the corals grow. I do not know if their is a max that can be tolerated. I think the only way it would be bad would be if you switched from a low PAR bulb to a high one with out acclimating the tank.

 

[Razor]

I'm currently replacing my Ushio 10K with new bulbs and noticed that in the tests conducted, they came up with a par value of 485 (Using a PFO ballast). In the same test the XM 10K had a PAR value of 600.

I'm considering going with a higher PAR value in my new bulbs but am concerned about frying my tank.

Oh by the way, you can see the tests at:

http://www.cnidarianreef.com/lamps.cfm

I thought he did a really great job with the variety of ballasts and bulbs he tested.

 

[Nautilus1]

As with any new bulb, as long as you acclimate the tank to the new bulb there will be no problem . The PAR on a sunny day, at noon with no clouds on the ocean's surface of a typical reef is a bout 2000 micro Einsteins. So 600 should be no problem. Furthermore, I did not see any distribution patterns of the PAR on the cnidarianreef link. The PAR of 600 is the value directly below the bulb. The PAR from a bulb will be the highest directly below the bulb. As you move away from the center the PAR value will drop off. So, only the corals below the bulb are going to be exposed to about 600 microEinsteins. Also, these measurements were taken in air, the PAR value will also drop off as you move down thru the water column.

 

[Anonymous]

Well yellower colors typically have higher par values, simple fact is a yellow photon of light is less energetic than a blue photon. So if your bulb puts out XX joules of energy if it's a yellow bulb you'll get more photons per second than if it was a blue bulb. Now how photosynthesis in animals work I'm not an expert at (although I do know how it works in semiconductors *grin*), but if I understand correctly they need just enough energy to produce "food" from light via a chemical reaction and any other energy is essentially wasted in the form of fluorescence. So bulb A has a more white spectrum, then it'll have more blue in it than bulb B) XM bulb which has more yellow to it. As a result more par, more energy packets available for photosynthetic creatures to make food.

Now you can have TOO much energy, stick any low light coral under really bright lights and you'll bleach it out in a hurry.

 

[Razor]

I understand that the PAR value will drop off with depth and because it is penetating the water, but I assumed if my coral were growing at a slow rate I could increase the PAR value to assist in their growth.

If I go from a Ushio 10K to a AB 10K, the PAR value will increase as will the growth of the coral who are currently not getting enough light. Those who are sensitive to light can be moved lower in the tank to compensate.

Right, or am I missing something?

 

[Anonymous]

I understand that the PAR value will drop off with depth and because it is penetating the water, but I assumed if my coral were growing at a slow rate I could increase the PAR value to assist in their growth.

If I go from a Ushio 10K to a AB 10K, the PAR value will increase as will the growth of the coral who are currently not getting enough light. Those who are sensitive to light can be moved lower in the tank to compensate.

Right, or am I missing something?

Lighting is just one piece of the puzzle. In addition, exceeding photosaturation can actually slow growth. Corals need to be considered individually, there is no one size fits all in my opinion.

 

[Razor]

Guy, what lighting are you running on your tank?

 

[Anonymous]

Guy, what lighting are you running on your tank?

Which tank?

My Main display has 3 X 250 watt HQI (Ushio 10,000K) + 4 X VHO Actinic (URI).

 

[Razor]

Perfect, same as on my tank.

What kind of coral are you housing in your large tank?

 

[Anonymous]

Water flow & quality will affect coral growth almost as much if not more than lighting as well.

 

[Razor]

Let me make that question a little easier.

I have the same 10K Ushios on my tank, but feel they're too white. So instead of runnig Actinics I was going to use a different bulb when it was time to replace these. In addition, the coral on the bottom of my tank doesn't get enough light, which is evident by the way they open and grow when being raised in the water column. Because I want to keep my current corals and also add some Stoneys, I figured I would get a blue bulb with a higher PAR rating. This would allow me to lower the coral in the water column, while still providing them with enough light on the bottom, clear space on top for Stoneys which require more light then my current SPS, and achieve a blue look.

Right or wrong?

 

[Razor]

Water flow & quality can be controlled and adjusted a little easier then lighting. You don't want to buy three $100 bulbs only to find out you purchased the wrong ones.

Sorry for the potentially dumb questions but this is the first time I'm changing my MHs and I want to make sure I'm buying the perfect bulb for my situation and taste.

 

[Len]

Both the XM 10,000K and Phoenix 14,000K DE bulbs are bluer then the Ushio and give more PAR. Color is important to us hobbyists from an aesthetic viewpoint, but IMO PAR and actual spectral output (not what we perceive) is more important to the health of your corals.

Until the website you referenced and even more so all of Dr. Sanjay Joshi's tests in www.advancedaquarist.com, hobbyists were left to trust the statements of the lighting manufacturers. Now we are equipped with a lot of useful information.

 

[Razor]

I was planning to go with the AB 10K, anyone have any experience with it?

 

[Len]

Yes. I actually like them a bit better then the Ushio. I found them a little more crisp white, but it could've just been quality control sampling differences. I still recommend trying XM 10K if you want the ice white look or Phoenix 14K if you want a bluish bulb.

 

[ChrisRD]

Razor, I'm a bit confused at this point - are you running Moguls or DEs? From your first post I got the impression maybe Moguls, but now it's sounding like DEs...

 

[Razor]

Moguls, why? Both the Ushio and the ABs I was mentioning are Moguls.

 

[ChrisRD]

OK, the mention of "HQI" and the Phoenix lamp threw me off (many people say "HQI" when talking about DEs...).

The Phoenix lamp is not available in Mogul style so that won't be an option (Len was probably thinking you had DEs too).

If you're running Mogul style lamps on an HQI ballast, I'm not sure switching from Ushios to ABs will get you much. Sanjay tested the color as slightly more yellow and the PAR as lower for the ABs on that ballast (although I know Joe's tests show the PAR as somewhat higher than the Ushios).

If you really want more PAR and a bit nicer look than the Ushios, the XM 10K might be your best bet, although I don't know how they do long-term on an HQI ballast (they're intended for a standard probe start ballast).

There are definitely some bluer lamps out there for your application, but nothing that will have the kind of PAR you're getting with the Ushios. Maybe going with a bluer lamp and a better reflector (to compensate for the lower PAR) you can get what you're looking for...

Anyway, not sure that helps, but FWIW...

 

[Razor]

The ballast I have is a PFO Standard not an HQI, would you still use the XM 10K?