Question regarding LED optics in deep tank

[novahobbies]

So, I'm looking at LED fixtures. Just curious at this point.
In a 29 inch deep tank, should I be looking at narrower optics than the standard 120 degree beam? I've had some people suggest 90 degree optics for this tank. Is it possible those might make too much of a "spotlight" effect on the sandbed?? Any thoughts would be appreciated!

 

[flower]

Deep tanks are difficult to light enough for corals all the way to the bottom. MHs and T5HO can't do it, I doubt LEDs could penitrate that deep either. There are plenty of corals that don't reuire the strong lights, so I always put those on the bottom of the tank and add the more light needy corals near the top.

 

[2quills]

Actually, you can fry some coral at 30" with leds if you really wanted to. They make optics that produce such a focused beam that if you put them on high powered leds you can turn them into lazers. But you are correct, Rick. The narrower the optics, the tighter the beam and the better the light penetrates into deeper water. But in the end it always comes down to what you are using and what you are trying to achieve. Typically 45 degree to 60 degree optics are a popular choice for tanks with those depths if you're looking for light demanding stuff on the sand bed. But you can imagine that the more you focuse the beam, the closer you will want to space your leds to help avoid the spotlighting effect. On the other hand I've been seeing guys use tighter optics in order to deliberately highlight/spotlight certain areas or certain corals within the tank and it looks kind of nice.

 

[flower]

Wow...I had no idea LEDs could be that powerful.
Now if they can just make some sort of replacement instead of toss away the entire unit...I would maybe switch over, so maybe in a few years when the systems get a little more perfected..

 

[2quills]

Yeah somebody needs to come out with a rig that's simple for everyone to maintain.
This stage light is a good example of focusing the output of an led. If I had to guess those are probably focused to around 5 degree beams (maybe less).

The typical leds used in the hobby generally produce about a 120 degree beam coming strait from the factory. So you figure if you put a 60 degree optic on that then you've focused the light by about 50%. That's like twice the PAR but in a smaller area. So you can imagine what would happen if you threw like a 15 or 20 degree optic on an led and focused it at a coral. You'd have the turn the output way down not to fry it if your goal was to spotlight one.

 

[flower]

LOL...what a light show..., I have blue LED moonlights, and they do have multiple colors available. Since my only real knowledge on LEDs are moonlights, it's pretty impressive to be able to get that much power out of them. I was thinking it just took hundreds of tiny lights to get the tank lit up, it never occured to me you could concentrate the beam.
I'm sure Novahobbies knows how to tune them way down for his purpose and needs. If I follow this thread correctly, you just confirmed what he was thinking. As for me...I'm properly impressed with the knowledge you guys have on such gizmos.

 

[novahobbies]

So Corey, would you recommend 60degree optics over 90?

 

[2quills]

How high are the leds going to be above the tank?

 

[novahobbies]

Honestly? Not high. 4 inches from the water surface, 5 max.

 

[2quills]

Off the top of my head I'd say stick with 90's if what you want to do is simply highlight your rock formations with minimal light spillage outside the tank. But without knowing what your build plans are I'd take that with a grain of salt. Technically you really don't need optics being that close to the water. It will be hard to blend colors if you use them. So tight spacing/grouping the leds together will probably be key to minimize any color/light banding in the tank.

 

[novahobbies]

Corey, thanks. I'll pass that on to the builder.
Now, I know you're going to smack your forehead and call me a heathen sinner. I'm going to be testing a Chinese 120w unit. I have read your points about the quality of the LEDs, workmanship, etc. I still want to test one unit on the horse tank; I may use them for the 110g tank, I may not....but I'll be posting detailed reviews on it when I get it in my hands, trust me.
On another note, my LFS has three of these over their 240g coral tank. They're happy with the coloration and polyp extension they're seeing, but they don't sell them directly because (of course) there's no warranty backup. This is all fine to me, but I'm also interested in LONG TERM coral growth....obviously the coral at the LFS doesn't stay in their tanks longer then a month.

 

[2quills]

I aint mad at ya, Rick. And I got nuthin against using the cheaper stuff. I just try to point out to folks some of the differences in products is all. I see a lot of references to leds as though they are all one and the same sometimes and it causes the hair on the back of my neck to stand up.

 

[novahobbies]

LOL Point well taken. No, I'm aware of the potential differences. One thing I'd like to do is post some "open 'er up" pictures if I can, as I'm skilled enough in my basic electronics knowledge to be sure I can open the case without ruining the unit completely. I figure if I'm going to take this plunge, I might as well document it for everyone to see the good, bad, and ugly when it comes to these units.