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Re: [APD] How much light actually gets down here?

Scott's reply is very good but just to add my  $0.10 worth (with the 
price of gas the price of my advice has increased).  If memory serves, a 
37gallon is 36x22x12, more or less.  So,  if you want to upgrade my 
suggestion would be either 1x96watt or 2x55watt PC arranged end to end.  
Either of those combinations would provide you with sufficient light to 
grow almost any plant, providing of course you meet the plants other 
nutritional requirements.  AH Supply makes excellent retrofit fixtures.  
They have the best reflectors on the market and the kits are easy even 
for a non-handy person to do.  The only real different between 1x96 and 
2x55 end to end is bulb  choice.  96watt bulbs are often more limited on 
color (k rating) than are 55 watt bulbs.  The difference in wattage and 
coverage is negligable in that case.   If you want to buy a ready made 
PC fixture I suggest the Current Satellite or Orbit.  Both are very 
nice, attractive and reasonably priced.

Another option is a 2 or 4x54watt T5HO fixture.  Tek (sunlight supply) 
has the best reflectors but the cost is more than for PC.  If you want a 
Tek but want to save some money, you can buy the "hydroponics" version 
which has 4 bulbs and 2 ballasts but only one cord and switch.  It is a 
very easy modification (for anyone) to add a second power cord if you 
want to control the bulbs independantly.  The hyrdoponics version is a 
good bit cheaper.   Personally, for that tank I would use a DIY setup of 
2x54watt T5HO.  A ballast is about $17 shipped, reflectors are $25 each 
and bulbs are $10-15 each.  You of course need to be able to build a 
hood and wire it.

T5 packs a little more punch the PC does and you get more light because 
restrike is minimized (thats why T5 uses special reflectors) in 
comparison to PC.  Either solution will proved you with enough light to 
penetrate 22" of water.  


S. Hieber wrote:
> There some easy answers, but they are at best just rules of thumb. 
> Answer 1) Measure it  with a PAR meter and numerous locations at the bottom, especially locations not directly under the bulb.
> Answer 2) Figure that the spectral output is reasonably good for aquatic plants and, after having gotten a lux value (which measure the lightfall on a given area) from the manufacturer or by measurement, roughly figure that the lux will drop proportionally with the distance (or as a square of the distance if the light was a point source instead of a line source). You have to figure roughly since a variety of factors come into play, including reflected light from the sides.
> Answer 3) Use watts per gallon as an ersatz standard and figure that changes in wpg will yield generally equivalent changes in how much light reaches any given area in the aquarium -- double the wpg, you'll double the light, other things being equal. When using wpg, figure that roughly 2wpg is medium, 3 or 4 high and less than 2 is low. But those are only guidelines since your actual results will depend on a wide variety of factors including, ambient temperature near the bulb(s), ballast, reflector quality, bulb spectral output, input voltage to the ballast, water clarity, the amount of etching that has occurred on the cover glass, et al.
> Answer 4) Watch your plants and gauge accordingly. Try more light if you want faster growth or to grow some of the plants that stubbornly require a lot of light. But keep you eye on the plants -- if you increase the light, be sure to keep tabs on CO2 and other nutrients -- they will be used up faster and if you don't keep up, you could provoke a burst of algae.
> Lastly,  65w should work well for many plants in most circumstances on a 37g tank. Put the more demanding plants towards the center and under the light source, other locations will tend to receive less light.
> good luck, good fun,
> sh
> ----- Original Message ----
> From: Erin Poythress <anang3 at yahoo_com>
> To: aquatic-plants at actwin_com
> Sent: Thursday, May 3, 2007 9:45:04 AM
> Subject: [APD] How much light actually gets down here?
> Hi everyone,
> Anyone know a reliable way to estimate how much of my
> 65W PCF reaches to the bottom of my 37G? The tank is
> 22" high and the legs of the light have it sit 1.5"
> above the glass lid (which is a necessity because of
> two very curious kitties). I tried to sit it flat on
> the lid, but the plastic joint got too hot for my
> comfort.
> Low-light plants grow reasonably well in there, but
> I'm considering an upgrade and wondered how much light
> would reasonably reach the bottom.
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