Watts per gallon

Twisted Melon

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How do you work out the watts per gallon for a set of lights?

I searched the forum but can’t find any info.

Thanks
 

Twisted Melon

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Sorry I should have said about setup.

I’m going for a high tech tank with led lights.

I only mentioned wpg because the manufactures seem to always list it, and I’ve only seen a few list the par values, but as I don’t have a meter to test it in my actual setup, it’s not that helpful.

Cheers for all the links! I’ll have a look at them now.
 

mow said

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tank size and led wattage i can help you with leds as i use them my self on my high tech set up
 

Twisted Melon

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I thought learning about CO2, flow and ferts was complicated! :banghead:

Without a par meter, how do I work out the light intensity at substrate level?

Seems I should be aiming for 50 micromols? Is it trail and error trying to get that?
 

ceg4048

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How do you work out the watts per gallon for a set of lights?

I searched the forum but can’t find any info.
That's because watts per liter or lumens per meter are irrelevant measurements. A decade or so it was the only guide we could use because PAR meters were (and to some extent still are) beyond the reach of most hobbyists and PAR was generally misunderstood. Any number used on a per volume basis is terrible because of the way light energy decays. The energy decay roughly follows the inverse square rule, so this means, for example, if you measure the energy at a certain distance from the bulb, the energy will be four times lower if measured at twice the distance. It will be nine time lower at three times the distance.

Volume does not take this behavior into account, because it has three dimensions (Length, Width, Height) from which the value can be increased, whereas it is only the Height dimension that really matters.

WPG is therefore a lottery because it is possible to have the same volume in tanks of differing Heights and the energy distribution will vary wildly.. Likewise, it can also occur that tanks can increase in volume but the Height may not increase proportionally, so it has happened that massive amounts of energy is thrown at a larger tank and the result can be devastating.

It is also a fact that the tall a tank is the more difficult it is to get CO2 (which is more important than light by a wide margin) to penetrate to the lower depth and traditionally, hobbyists have ignored this, most important factor. So as you can imaging, the combination of excessive light energy plus the habit of paying poor attention to CO2/flow/distribution led to the recurring issues of poor plant health, which then leads to algal blooms.

When shopping for LEDs therefore, it is always a wise choice to ensure that the PAR levels are published or otherwise known by other hobbyists, and if possible, a controller that enables you to limit the output is available.
When shopping for a T5 or T8, typical PAR data is available such as this:
PARforVariousBulbs.jpg


So the idea is to limit the number of bulbs so that you can stay in the blue zone if possible, especially when starting the tank, and only stray into the pink and yellow zones when CO2/flow/distribution is good.

Cheers,
 

Twisted Melon

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Cheers ceg.

So if I’m reading that correctly, 1 x T5HO needs to be just over 25 inches from the substrate to be in the blue zone?

My tank is only 16” deep. I’m struggling how to work out what I’d need to get going by that graph. Could you give me s pointer please?

Thanks again.
 

ceg4048

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So if I’m reading that correctly, 1 x T5HO needs to be just over 25 inches from the substrate to be in the blue zone?
Yes, that is about right.
My tank is only 16” deep. I’m struggling how to work out what I’d need to get going by that graph. Could you give me s pointer please?
Well this is the problem that arose as a direct result of the emergence of T5 bulbs in the 1990's. If you look at the T8 curve it was very forgiving and multiple bulbs could be used without any worry.
If you have a single bulb T5, and if you are not using CO2 via gas or liquid, then there are simple ways to reduce the energy. For example, floating plants can be used to reduce the penetration. If your tank has a glass lid, wax paper can be used on top. It's just a matter of using your imagination to find ways of blocking some of the light.
The problem with using a single bulb though is that the spread isn't very pleasant. It would be much better to use a couple of T8s.

Cheers,
 

foxfish

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LEDs have only been popular for the last few years, before that, 2 x T8s the length of the tank for low tech & 2 x T5s the length of the tank was the recommended for high tech.
Before T5s.... 2 x T8 for low tech & four x T8 for high tech.
During the early days of this forum, T5s were really popular. Most folk, found great success using the standard recommendations but of course there were the few who had everything right & could use 3, 4 & even 6 x T5s.
Mercury Vapour hanging lights & even Metal Halides have been used but you were always on the edge with these!
I can remember a time when the new generation of household 12 volt down lighters became popular (maybe 30 years ago) & they were tried as well.
For me, I still favour T5s, however I have problems using my TV remote , so I guess I am old tech in myself!
 

Twisted Melon

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I don’t really have a favourite at the moment between led and tubes. I’d happily get either.

I do like the controllability of leds. Especially being able to dim them.

Finding the PAR values for leds is proving a bit of a pain though to be honest.

I’m considering either Kessil a160we tuna sun or the Fluval plant 2.0. I’ve found the PAR for the Fluval but not the Kessil. Only that it drops sharply outside 45-50cm.

Plus I’d need 3 Kessil which is kinda expensive!!
 

alto

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@ceg4048

Any origin or source on that light chart - it's ubiquitous but I've yet to find the "Materials & Methods"
 

alto

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For some reason Kessil requested removal of non-affiliated PAR data - you might request information from the company
(Sanjay Joshi had included Kessil in his light analyses)

Giesemann also withholds this information (& has proffered reasonable explanation)

T5 is definitely lower cost, though if you want even light distribution across the 45cm tank width, there are some considerations

I've been running a 60cm x 45cm x 55cm (height) with a T5 fixture, finally switched (temporarily) to a Kessil A160 (the A360 would provide more even coverage if I were buying a light for this tank) & really prefer the access & dimming control etc, plants seem well enough though there are some shadowed areas that need to be taken into account- I adjusted hardscape etc
 

mow said

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the best way to test led without par meter is lumens per litre but you still wont have a clue what the par value is. What i would do is start of with 5 hours 50 percent power if its too much then lower it and if you do not see any algae and plants are growing as you want them to then leave it as it is. Once the tank has more plant mass then increase the the time to 8 hours and intensity. If you have any problems with algae then you know your light is too much. Take your time as too much light do cause algae and many other problems. I built myself an led light and i have a good understanding of how much light i need to use when i use leds without a par meter.
 

Tim Harrison

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I prefer the colour rendition of T5s, especially the combo of Arcadia's Freshwater and Plant Pro lamps - they really make critter and plant colours pop - nothing I've seen in LED comes close.
Although, the new ADA LED - Solar RGB - is supposed to be pretty good; it costs an arm and a leg tho'.

The best way forward with LED is to buy something that is controllable/adjustable - with at least a dimmer - and start off with moderate light, like mow mentions above, and go from there.
 

ian_m

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You can get a rough guide to work out if your new LED fixture is going to be high, medium or low light for your tank volume get a rough idea of watts per gallon.

You should be able to get a lumen output for your LED fixture, either quoted by manufacturer directly or look up the lumens per LED and multiply by no of LED's. If light is from China or Ebay and not a well known name divide the lumens by at least 2 maybe 3 or 4 as they do tend to overstate the lumen outputs. ;)

Good quality reputuable makes (Arcadia, Juwel etc) T5 HO tubes generally produce about 60lumens per watt (considerably more light than cheap LED fixtures of course).

Thus you can get rough T5 wattage ratings for your LED light.

Then work out tank capacity in US gallons to workout watts per gallon. This generally assumes the tank is a "typical ratio" where depth is approximately equal to width. Obviously very deep and very wide tanks the Watts/gallon doesn't hold.

Anything above 2W (T5) / US gallon is high light region. Below 1W / US gallon is low light.

For example my tank is 180litres with either 2 or 4 T5 35W tubes.

180litres is 50US gallons.

My T5 lighting is 70W or 140W, thus I get 1.4W/G or 2.8W/G. So four tubes, as I know, are well in high light requiring spot on CO2 and EI dosing and frequent plant trimming and water changes.

This is all a rough guide, to be used in conjunction with cegs graph, to allow you to work out the rough magnitude of tank maintence, CO2 injection perfection, ferts dosing and algae growing you will be heading for.

Generally from my experience a single T5 tube in a typical "ratio tank" (ie depth about same as width) with maybe some foil rings on the tube to reduce light levels (and/or no reflectors) will be classed as low level.
 

Twisted Melon

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I've been running a 60cm x 45cm x 55cm (height) with a T5 fixture, finally switched (temporarily) to a Kessil A160 (the A360 would provide more even coverage if I were buying a light for this tank) & really prefer the access & dimming control etc, plants seem well enough though there are some shadowed areas that need to be taken into account- I adjusted hardscape etc
Is that just the 1 a160 you’re running on that rank?

Cheers
 
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