Can someone explain Low and high light needs?

Let me add another comment here to make things more confusing...

I think it also depends on the depth of your tank. 1.5WPG will be medium if your tank is only 12" deep or it could be low if your tank is 20" deep. It could be even lower if you like to suspend your fixture 6" above the tank...
 
Great link. You can grow some plants in a 10g with only one 15w bulb, but a minimum of 30w is a good starting point. So basically use the wpg rule with a min. of about 30w (for small tanks) of appropriate lighting and you should do fine.
 
How does one know the LUX of ones light? Rex's site doesn't go into detail about this and I've checks my lighting docs for said term without success.
 
I am a little concerned that the Dwarf Sag I bought today won't live in my ten gallon tank though. It has a flourescent 15 watt light over it with DIY CO2. Would it live?
 
Slappy*McFish said:
http://www.electronickits.com/gold/lt2101.htm
Click to expand...

Thx for the link... However it seems counter intuitive one would need a monitoring device to gauge a store-bought lighting system.

Also, provided specs of the lighting system (in my case, 4 x 65 watts @ 10k), one should be able to 'ballpark'...

Also, one should be able to also accomodate for the distance from the bottom of a light to the surface of the water.

About the only thing perhaps difficult to describe is the reflective surface above the lights and how it affects LUX. But I imagine it too can be fudged a tad... For example my 'reflective surface' suggests it to be highly polished perhaps to the extent that say, 85% of total lighting output is reflected into the water.

I suppose bottom line is that there should be a mathematical formula 'out there' which describes this WITHOUT having to buy a tool.
 
it can get pretty complicated as the wpg rule is not effective for small tanks or large tanks..

I say throw some light(daylight bulbs) over the tank.. toss in some plants and then see what happens. ;)
 
I'm going to work on making the number fly.

Rex's page is relativly informative but leave a bit to be desired.
For example, there are a number of tank sizes mentioned but none reference the surface areas - trying to back into 'the numbers' is difficult.

For example, this doesn't make sense... The idea is to derive an LSI ('thing' as he put's it) but, you're asked to arbitrarily plug in a desired LSI ! And finally, after you've done the math, you don't know what you are actually striving for!

"Now I know what you are thinking. I can do watts per gallon pretty easy. But how do I figure this LSI thing? Well find the surface area of your tank in square inches. Then take the LSI number you want to reach. Multiply the surface area by the LSI. Take the result and divide it by the LUX rating of your chosen light. I will admit that this system is not perfect by any means. But I think it gives a better idea than the WPG rule."

I've a dialog stared with Rex to better understand the above.

In any event, back to some of his examples and tank size.

Searches on the net for a 55 gallon tank dimension seem to return:
"47.5 inches long, 12 inches wide and 19 inches high (all inside dimensions)"

The math suggests 570 square inches of surface area.
Take this and multiple by your desired LSI... An interesting comment... Because, LSI should be LUX (lumens per square meter) divided by 39.4 (lumens per square meters to lumens per square inches)... So what are you really figuring out here?

Anyway, 30 as an LSI seems a good 'grow anything' number... so, 570 * 30 = 17,100.
Unfortunately Rex doesn't provide the LUX in this example but if the 39.4 figure holds true, LUX (lumens per square meters) is about 434 (17,100 / 39.4) ?

Hmmm... Seems rather than to "Then take the LSI number you want to reach. Multiply the surface area by the LSI" you would instead factor in your LUX...

Confusing...
 
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