Lighting Part 3 Metal Halide - Podcast Episode 77

[Rob]

Part 3 in the lighting series.
Ok, here we go with the MH show, in this show i discuss what the MH bulb is and how it works

Topics:
- Plasma
- Halides
- Bulb
- Arc Tube
- Fireing and burning
- how the light is produced and changed
- why a cool down period




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[rroselavy]

Great intro to MH.

I first thought the fluorescent show was a touch too geeky only when you started discussing the activity of electrons with your journey down the center of the tube (with a 90 degree turn to describe it's section). I was left thinking to my (simplistic) self, "Isn't it sufficient to say that the gases get charged and cause the phosphorous coating to react?".

However, The MH show really sparked my interest. I had no idea that there was an arc that ignites gasses to form plasma. That's really cool. The bit about the bulb cooling down before firing again makes perfect sense, as does the fact that the gasses/metals/minerals become depleted which alter the light that the bulb creates over time.

Very well done. Perhaps I was wrong about the fluorescent show being too geeky; My lack of knowledge of MH proves that it is never inappropriate to cover the fundaments.

[Rob]

thanks.. im glad you found them helpful.. i was trying to only include the info that was relevant to understand the equipment, and that would be needed to explain the stuff to follow, as you can see since there is a difference in the way they two types are "lit" i thought it would be important to describe them..

[Warnberg]

Rob, great series on lighting. Couple of things I like to see you cover, first what are recommended distances for different bulbs from water surface and why, also recommended photo periods for different bulb types and why. Might also want to mention monthly operating expenses of each type of bulb.

Keep up the good work.

[Driftwood]

I like the lighting series so far. Lots of interesting reefgeek info that I can soak up.

A few things that I am curious about are:

What do you use to determine the best setup for your reef? Is there really a true and tested watts per gallon standard? What ammount of lighting is needed for deeper tanks, like 30 inches? Is there a good way for someone to determine how high in the tank to place a certain creature with different ammounts of lighting?

These questions may not really have specific answers because every system is different, but they are questions that reefers have everyday. It would be nice if someone could come up with some math that would make this easyer. Each coral could have a recommended light range and you could calculate what your light rating was by taking into consideration your lights and depth...

Anyway, best of luck on the next show!

[stevfam]

Rob,

Sorry about the tank... a lot of lessons learned for all of us. Here's to a quick recovery...

The lighting shows have been excellent, especially the MH discussion. Makes a lot more sense now.

I was wondering if you could discuss the difference (if any) between the 420nm Actinic and the 460nm blue bulbs. I use 2 65W PC actinic lights to supplement 2 250w MH on a 90 gallon SPS tank. I'm about due to replace bulbs and I was curious if there was a major difference between the two options. Both seem to work similarly with the 460nm bulb being a little brighter.

Just a thought.

Thanks

[CarmieJo]

Hi stevfam,

to TR.

[Pinecone_Jeff]

Ok, I'm finally all caught up with all the episodes! I've listened to them all! Woo Hoo!!!

I'm really dig'n the lighting series right now. MH lights don't seem to be so mysterious anymore.

Here's a question for ya. Since PC or VHO bulbs need to be relatively closer to the water surface than MH bulbs, aren't you losing a lot of light with those systems that have both MH and flourescent actinics in them? How do you get around this? Or does it even matter if you main lights are MH?

Thanks!

Jeff

[Astrivian]

Okay, i have a question as well Rob Is there some reason one would choose HQI dual-ended bulbs over single ended ones? You talked a bit about them but i am still wondering, from the DIY standpoint, if i should go with one or the other.