# How much ligh to aim for in a nano.



## Krishs Bettas (5 Jun 2010)

Holw much do you think I should aim for in a 30litre tank? To grow HC in?


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## scifficus (5 Jun 2010)

Depend on how high is your tank. I use a bulb with _900_ lumens on a 12 liter net nano. With de height of tank and the loose of light outside the tank , my Cuba has a good growth.

PS you'll have to look for the lumens, not the wattages. A good ratio ( teoretical ) is over 60 lumen / liter.

Here's a not clear good picture.


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## Garuf (5 Jun 2010)

Lumens is visisble light not PAR which is what you are actually aiming for. 1wper litre is a good rule of thumb for anything up to about 10gallons.


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## scifficus (5 Jun 2010)

The rule of thumb is lumen per liter, because two different fluorescent tube at the same watts is possibile to have different lumens. If everyone have a PAR meter or something to measure that i'll be ok, so per general the apropiate number to look for it will be the lumens and the spectrum, obviously.


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## ceg4048 (5 Jun 2010)

Hi,
   Lumens are an illusion and so is the concept that HC requires lots of light. I always wonder whether Lumen lovers actually understand what a Lumen is. The fact of the matter is that plants don't know what Lumens are either and they don't respond to it. They respond strictly to PAR.

If you are assessing bulbs on the basis of brightness then it's always better to compare bulbs of similar technology. In this way the wattage rating becomes more relevant. So for example it's not a good idea to compare the wattage of a T5 bulb with the wattage of an LED because each delivers it's radiation differently. However, one can certainly compare an 11 watt T5 bulb with an 18 watt T5 bulb. It's clear that due to similar delivery methods, it's a good bet that an 18 watt T5 bulb generally delivers more photonic energy than it's 11 watt cousin.

The conventional rule of thumb has always been watts per gallon or watts per litre as far as I can remember. Some argue whether this was based on T5 or T8 or even T12. Since T5 became the de facto standard for high tech tanks we are more or less calibrated to think in terms of comparing T5 bulbs. As various bulb technologies become in vogue however, the water has been muddied somewhat.

In any case, neither wattage nor Lumens tell the story, unless someone can chart a given bulb on a graph that will show it's Lumens versus PAR. You'll find that there is zero correlation between the two, therefore using a Lumen value is strictly a matter of luck. Bulb X can be rated at a higher Lumen value than Bulb Y, yet, Bulb Y can at the same time deliver a higher PAR and generate a higher growth rate (and algae) than Bulb X. Lumens therefore is a very poor standard of measurement to use generally.

As far as the OPs question, a 7 gallon tank does not need more than about 10-20 watts T5 to grow HC. But HC appreciates good flow and CO2, which are 100X more important than watts or Lumens. HC can grow in just about any light but higher light generates higher growth rates. These higher growth rates will require better nutrients, CO2 and flow.

Cheers,


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## dw1305 (8 Jun 2010)

Hi all,
As suggested "lumens" is a totally useless as a measure of PAR. However I love lumens, how can you not like a unit based on the "foot-candle", 





> One of the best-known of these was the English standard of candlepower. One candlepower was the light produced by a pure spermaceti candle weighing one sixth of a pound and burning at a rate of 120 grains per hour.


 Rather than consigning the whole candela/lux/lumen to history along with span, groat and perch the International Commission on Illumination decided to make it an SI unit, no I don't understand why either, maybe they have a sense of humour?

cheers Darrel


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## paul.in.kendal (8 Jun 2010)

Aah, wonderful stuff, Darrel - UKAPS broadens my mind yet again!


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