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RE: [AGA-Member] RE: Lighting

Wow, Scott, that's good stuff to know. My problem with metal halides is that if you only have one, like I do on my 29G, the light has trouble reaching the sides and underparts of my corals. I have experienced some localized bleaching due to this. I imagine the same thing might happen with plants. My compacts spread across the length of the tank and give good lighting.

From: "shieber" <aga-member@thekrib.com>
Reply-To: Aquatic Gardeners Association Member Chat <aga-member@thekrib.com>
To: aga-member@thekrib.com
Subject: [AGA-Member] RE: Lighting
Date: Thu, 05 Jan 2006 05:29:54 -0800

Good points, Heather. I'll offer a few comments.

Heather Gladney wrote: > . . .compact fluorescent bulbs . . . > I find them reasonably powerful for the cost, and they last longer and > are not nearly as much thermal burden as metal halides would be. . . >

As commonly applied, MHs present less heat ("thermal burden" ?) to an aquarium than fluorescents. Metal Halides have very close to the same energy efficiency as compact fluorescents -- often slightly better. So the amount of input energy that is given off as heat is the same (or slightly less) with MHs compared to CFs -- roughly 65% of the input energy is shed as heat rather than visible light. In operation, MH bulbs usually have a higher local temp than CFs -- the heat is concentrated in a smaller area, but the concentration doesnâ??t present a special thermal burden. MHs are usually suspend higher above the aquarium than CFs -- so that more of the light will reach across more of the length of the aquarium -- with the result that more the heat goes directly into the room instead of going into the aquarium first.

Heather Gladney wrote: > That said, they do not punch down through great depths as well as I'm > told halides would, and the light quality is shadowless & diffuse. . .

Halides illuminate from a small arc inside a small bulb, often described as a 'point source' of light. So the light does not distribute along the length of an aquarium and at any given position in the aquarium, an object is struck by light of a MH from one direction -- which gives sharp shadows, twinkly water, etc. Fluorescents illuminate from virtually the entire inner surface of the long bulb -- often called a 'line source' but "tube source' which be much more accurate since the "line" has considerable thickness. A Fluorescent distribute light along the length and striking an object from several sides, soften shadows, as if hundreds or thousands of very tiny lights where shining on each object from as many diff directions.

MHs are usually more expensive to maintain than fluorescents, although newer designs aren't quite as prone to the terrible color shifts in output that used to make MHs close to useless in the space of a year. And if one hunts, some bargains can be found.

Heather Gladney wrote: > On fans, . . .somebody. . . might have mentioned some good fan sizes & > mfr names for durable, high-quality, very quiet fans for use with light > kits etc. > RE: other types of lighting, I'd love to know if anybody knows of > someone trying the newer LEDs, and what the results were. . . .

Mouser.com lists a wide variety of fans along with the specs provided by the manufacturers. Take the specs with a grain or salt; they cite ideal operating conditions. The prices there (although not the prices everywhere) will give a good indication of which manufacturers make the higher quality fans. Any of the fans mouser sells would be reasonable for aquatic gardening purposes.

Be wary of claims of high airflow or very quiet fans. One is a trade off for the other and honest vendors are unlikely to claim both features for the same fan. While there is some variation in quietness and airflow between diff models of fan for a given size, usually it's a matter of trading off airflow for quietness or vice versa -- in fewer circumstances, the diffs are due to diff testing conditions or extraordinary optimism ;-)

The tips of the fan do almost all of the work and the area of a circle increases geometrically with arithmetic increases in diameter. So a slightly larger fan can move more air than a slightly small one while spinning more quietly at lower rpms. If you need to use fans, as rules of thumb:

use the largest one you can fit;
use the slowest ones that have the required airflow;
use ball bearing fans rather than sleeve bearings -- although sleeve bearing fans can be quieter initially, they tend to age faster and as they age, they can become louder.

Personal computer supply stores usually hoave lots of computer cooling fans to choose from that will work for aquarium lights. The computer sites will refer to the fans as "case fans." Generally, they will be presented with marketing kudos and few specs. [Wink]

Re LEDs. To be feasible, one would need to use the relatively new, high output 'super bright' LEDs. Compared to "regular" LEDs, these come in a variety of colors, allowing for a broader and fuller spectrum with a carefully chosen array. Unfortunately, the super bright LEDs rely a method of fluorescence and generally have no better (usually worse) energy efficiency than fluorescent lamps. The LEDs have durability in their favor but they cost more to set up and, being less efficient, cost more to operate. The future of aquarium lighting, imo, is unlikely to shift towards LEDs.

Scott H.

Scott H.

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