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Discussion Starter · #1 ·
I just setup a 20G Long aquarium using a LED light. I've never used LED lighting before, only compact flourescents. So I'm not familiar with WPG rule with this type of lighting. I'm wondering if the light fixture I have is significant enough to grow low light plants? This is what I have...

Current Satellite Freshwater LED
10 watts, 12V, 400 lumens
6500k white (66 leds)
445nm blue (24 leds)

Any help appreciated!
 

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Based on http://current-usa.com/wp-content/uploads/2015/04/Satellite-Comparison-V3.pdf you probably have less than 20 PAR light intensity, which is too little for almost all plants other than mosses, Java Ferns, anubias, and a few of the "weedy" plants like, perhaps, Hydrophila polysperma. I found that it took me about 35-40 PAR before I could grow most of the low light plants. You could use two of those lights, and you would have plenty of light for a low light tank.

There is no watts per gallon "rule" using LED lights (actually there is none for any type of lighting other than T8 lights). You have to go by measured light intensity using a PAR meter.
 

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Discussion Starter · #3 ·
Thanks hoppy... I was thinking about buying a 2nd light fixture, now I definitely will. I knew it did not look very bright.

Could you suggest a single LED light fixture that would be better than 2 of the ones I already have, that don't cost a arm and a leg?
 

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A Finnex Planted Plus 30 inch light should give you roughly twice what that light gives you, which would very likely be low medium to medium light. If it is a Planted Plus 24/7 light it could be dimmed if you need to do so. (And, later, when you decide you want to use medium light plants it would work for that.) At $85 I agree that it isn't the most economical light.

Incidentally, without actually measuring the light intensity any guess about how much light you have is just a guess. Now it is possible to borrow a PAR meter and find out how much light you really do have. Hint: there is a forum here where you can get stuff like this from other hobbyists.
 

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I would suggest the 30" EA beamswork 6500k .5W led and you can get their timer to go with that all for 45 bucks shipped on eBay, I have the same setup and it works perfect. It's bright enough to provide a good lit tank and has enough par for low light plants on a 20 long.


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Discussion Starter · #6 ·
Thank you both for the suggestions. I decided to go with another current fixture like the one I already have.
 

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I got a PAR reading of about 400 at the water surface just 2.5" under this fixture, which has ~142 diodes. Some of the other 30" Beamswork have only 42 diodes; for them I measured only 200 at the same position. I used a high quality PAR meter (Apogee) that was lent to me by the local aquarium society.
 

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I got a PAR reading of about 400 at the water surface just 2.5" under this fixture, which has ~142 diodes. Some of the other 30" Beamswork have only 42 diodes; for them I measured only 200 at the same position. I used a high quality PAR meter (Apogee) that was lent to me by the local aquarium society.
Most plants start their life at the substrate, and it is during that early growth period that plants either grow well or don't grow well. Based on that it is much better to measure light intensity at the substrate, not at the water-air interface. If you have a tall tank, like a 20 high tank, a high PAR reading at the top of the water column, with the light sitting on top of the tank, doesn't mean you have adequate light at the substrate. And, a high PAR reading at the top of the water column can mean much too much light at the substrate, if you have a low tank, like a 20 long tank. I suspect that some day someone will come up with a better way to use a PAR meter, when choosing a light fixture, but for now I strongly suggest always going by the PAR reading at the substrate.
 

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Most plants start their life at the substrate, and it is during that early growth period that plants either grow well or don't grow well. Based on that it is much better to measure light intensity at the substrate, not at the water-air interface. If you have a tall tank, like a 20 high tank, a high PAR reading at the top of the water column, with the light sitting on top of the tank, doesn't mean you have adequate light at the substrate. And, a high PAR reading at the top of the water column can mean much too much light at the substrate, if you have a low tank, like a 20 long tank. I suspect that some day someone will come up with a better way to use a PAR meter, when choosing a light fixture, but for now I strongly suggest always going by the PAR reading at the substrate.
Yes, but you should be able to calculate PAR at the substrate based on surface measurements. As light passes through a certain distance of water, it loses its intensity in a straightforward way.

I have established tanks so overhead light is absorbed by floating plants and plants already in the tank. So substrate measurements are misleading, especially since I now have bare glass bottoms with plants in pots.

That said, I measured about 5-20 PAR at the glass bottom of my 20 gal Long (12" high).

Lighting is complicated. We could split hairs all day, but I hope the information that I have provided will be useful.
 

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@Hoppy is right on PAR!

Measure @ the substrate.

Floating plants typically get full sun, doesn't matter much to them.

Shading can be the downfall of many plants.
 

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Hi... In the event that cash is the restricting element, at that point I would genuinely consider a modest T5HO installation first off and keep on seeing what LED you may need. Driven looks better, T5 is simpler to arrangement and develop corals. Driven works much better with more pucks and the splendor diminished, instead of only a couple pucks turned far up. Hotspots can be a genuine issue when you need more spread.
 

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Excuse me, I'm fumbling around trying to decipher the lighting choices today for planted tanks, LED, T5, T8 etc, etc, and it seems to me that every T5HO fixture I've run across so far has been quite a bit more money than any of the many LED fixtures available for the same size tank. I think the second part of your post is saying the T5's can look better, but the T5HO's seem to be a couple 100 dollars as opposed to around a 100 for a good LED set up for a 20G. Or what am I missing here? Thanks.
 

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The old fluorescent technologies (T5, T5HO, T8, SCF, etc.) are obsolete. LEDs are better for function, efficiency, and environmental impact. The problem with LEDs is confusion, over-choice, and the manufacturers' stubborn refusal to adopt a uniform and comparable measurement of light quality and intensity.

For most of us, the best way to make a choice is to describe our set-ups (tank size, desired plant species, and budget) and ask for recommendations here. Yes, you will get some off-the-wall answers. But keep asking and eventually a consensus will emerge.
 
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