D.E. vs mogule question

[mattboy]

Hi;

I posted this in advanced topics, but copied here. This is probably the best forum for this question

I'm planning on moving, and setting up a 100 gal reef to replace my crowded 45 breeder. I'm considering D.E. pendants, and have a few questions.
1. Would a couple of mini-pendants, maybe 250W, throw less heat than 250W mogule set-ups, assuming they're both hung above an open tank?
2. Are 150 W pendants comparable in PPFD output to 10000K ushio 250W mogule bulbs, again, assuming a similar mounting situation? Or would 250W D.E. be more appropriate for a 100 gal (60"X18"X21")
3. Is there any way to get these D.E. set ups without paying $325+ for each pendant?

Currently I have 2 175W ushios over my 45. I love the light; it gets a bit warm in the summer, but managable.

Thanks in advance, Matt

[Nanook]

I have a couple of the PFO mini pendants that house the 250w DE bulbs...I think they run hotter than 250w 10Ks....but have never put my hand on them very long:D

If that was my tank, I would use Spiderlight or some other parabolic reflector and mount a couple of bulbs perpendicular to the tank front. Ideally, a metal halide bulb will cover 2 ft...you can mount them perpendicularly and cover 2.5ft OK in my opinion. The mini pendants lack a bit of lightspread capability compared to a large parabolic reflector in my opinion. FWIW,


Nanook

[piercho]

"Are 150 W pendants comparable in PPFD output to 10000K ushio 250W mogule bulbs, again, assuming a similar mounting situation? Or would 250W D.E. be more appropriate for a 100 gal (60"X18"X21")"

150W DE bulbs won't produce as much light (at the bulb) as a higher wattage mogule bulb. Some 150W DE reflectors may produce as much intensity at the water's surface as larger wattage mogul bulbs in parabolic (like spiderlight) retrofit reflectors when mounted at a similar distance from the water.

How much light a reflector actually gets into the tank is a subject that is just beginning to be broached. Read Sanjay Joshi's article on retrofit reflectors in the March issue of Advance Aquarist (online) magazine. Also, look for Harker's two articles comparing PPFD of a 150W DE bulb to a mogul bulb, with and without reflectors, also in recent Advanced Aquarist articles.

Joshi's upcomming article on the effectiveness of pendant's should be out soon. My gut feeling is that most of us will get an education on just how good DE pendant's really are at getting light into the water. Anyway, it is that upcomming article that will provide empircal answers to the questions that you are asking here.