# Light bulb comparisons experiment



## dawntwister (Sep 29, 2007)

This is a 29 gallon tank. I have been changing my lights. Thought results would verify that the photons are more important than the wattage thus posting results.

Growlight bulb 20 watts and Philip T8 daylight bulb 20 watts









Dual PC 10000k/6500k 65 watts and Philips T8 daylight 20 watts









Philips T8 daylight 20 watts and Zoo Med T8 super daylight 20 watts after 2 wks









Zoo Med T8 super day and Life-Glo 2 T8 bulb pending


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## Dryn (Sep 6, 2007)

The pics are kinda hard to see well. You should be looking for better, thicker growth. To measure, you would have to cut a certain amount (probably length) of plants from each tank, dry them, and then weigh them to see how much mass was made in a specific length of time for each "expirament" tank, alongside of a control tank with "normal" light (probably daylight?).

We don't see the same light that plants do, so a visual inspection, or one based on degrees kelvin, lumens, lux, and/or CRI would not do us any good if we were trying to find out what light is better for our plants.

You mentioned photons, and that is on the right track, but good luck measuring them, those buggers are small!  All kidding aside, not all photons are equal, but for plants, the range of photons (from 400nm to 700nm) are relatively equal in needed amounts for a mixed community of plants depending upon placement. There is a lot of controversey and speculation involved in the measurement of photons and which ones are better and at what specific wavelength, but it evens out in the end.

Yeah, plants don't use green light (which we see best) as well as red light, or even blue light but they still use it. They just need more wattage. From my studies, I've come to the conclusion that One watt of power is very *roughly* translatable to at least 1 microEinstein/m^2(m^2*s) (or photosynthetically active radiation, better known as the bajillion photons that plants see broken down into a number easily digestable). There is a variance of as much as +0.4/-.2, which makes this measurement virtually meaningless,  but still better than the usual watt per gallon measurement when you're trying to calculate how many usable photons are being sent out by your tank.

Of course, once you have the number of photons (microEinsteins/m^2/(m^2*s) per watt measure from the source, then you have to calculate how many photons ( microEinsteins/m^2/(m^2*s) are lost by the relflectors (50% for poor relflectors and 10% for good relflectors), how far from the water surface (inverse square law), the water refraction according to how turbulent the water is (as much as 33%), just to roughly calculate how many photons (microEinsteins/m^2/(m^2*s) reach into the water! WOW. 

That is definately a lot to calculate, but it isn't done even then.  You would have to calculate how many photons 'fizzle' for each inch of depth (very roughly 17 microEinsteins/m^2/(m^2*s) per inch) but dependent upon how "direct" the light source is. When you get how many photons are reaching each strata of the tank, you then have to calculate what the plants need!

I've found out that plants need "roughly!" 15-80 microEinsteins/m^2/(m^2*s) for low light plants 50-100 microEinsteins/m^2/(m^2*s) for high light plants and 80-150 microEinsteins/m^2/(m^2*s) for high light plants or more! To make things just a bit more complicated if you don't already have a headache, light filtered through the leaves drop you some 80%, a painted on background reduces you some 33% near the glass, and the glass itself reflects _Back!_ some 10% of light to add back to the calculation! I hope your head is still on at this point, but you did ask.

Once you manage to do all of those calculations, you could still be very, very far off. I've done the calculations on a few dozen tanks, checking against a PAR meter (which measure the amt of photons in the plant-usable range) and found myself off by about 10-50 microEinsteins/m^2/(m^2*s).

Even if you decide to skip the calculations and fork over about $350 for a PAR meter the meter measures all of the photons in the usable range without making allowances for the excessive photons that cannot be absorbed by the plants.

It is much easier to use the wpg rule of thumb. The photon-measureing rule of thumb is very, very complicated (and I left a lot out) and not really any better. I do hope that I've helped somewhat, and I offer anyone to talk with me about this if they want.


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## dawntwister (Sep 29, 2007)

Dryn said:


> The pics are kinda hard to see well. You should be looking for better, thicker growth. To measure, you would have to cut a certain amount (probably length) of plants from each tank, dry them, and then weigh them to see how much mass was made in a specific length of time for each "expirament" tank, alongside of a control tank with "normal" light (probably daylight?).
> 
> It is much easier to use the wpg rule of thumb.


What I am mainly observing is the change in the Hygro sunset with the bulbs I have. Uncertain which will bulbs I will use.

Are you aware that the wpg rule is based on T12 bulbs.

Also people like Trallen44 have proven you can have great growth with less than 
1 wpg.


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## Dryn (Sep 6, 2007)

What I was getting at was that there are many ways to calculate how much light you need and all can be successful, but none are universal. For all intents and purposes, the wpg is a good rule of thumb. But it is just that - a rule of thumb.


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## dawntwister (Sep 29, 2007)

This thread is just to show the comparisons of the T8's I have to the higher wattage light that I had. Hopefully the result will show that I can get the same growth with 2-20 watt bulbs that I did with the higher wattage.


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## Supercoley1 (May 28, 2007)

I've been saying that for a long time. You won't convince the majority here believe me 

It ain't about the amount of light supplied alone. Spread is the key thing and 4 x T8 equal to 2 T5HO in wattage can provide a much better spread.

I am now expecting the usual belittlings and Lumens quotes. lol

AC


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## dawntwister (Sep 29, 2007)

Supercoley1 said:


> Spread is the key thing and 4 x T8 equal to 2 T5HO in wattage can provide a much better spread.


Now I am wonder if I should move the bulbs. I have 2 compacted into a metal tube over the area where a light strip goes over the hood.


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## Supercoley1 (May 28, 2007)

People tend to look at things with only science and mathematics in their heads where as many aspects of the aquarium show they often don't follow the 'general' rules 

For example people think the closer the light is to the water then the more light will be there for the plants and raising it up will reduce the light. This is true to a point but IMO this is more a balance like a focus on a camera. The focus isn't as close as you can get . It is blurred then you reach the best focus and then further away is blurred again!!

With light I think that as close as you can get limits the spread, move away a certain amount gets peak spread and then further away again reduces the amount of light (but not the spread of this remaining light.)

Power and Lumens are worthless measurements for working this out accurately. They are just measurements of power and how bright a light looks to the human eye. K ratings are worthless in the planted aquarium although many still harp on about reds and blues and greens. Many planted tanks do fine under 'supposed' green lights but in truth virtually all lights including the marine ones actually supply enough of all colours for the plants.

There are also papers detailing tests of plant growth under dedicated green light and the results disprove the 'plants can't use green light theories'.

The only way to properly measure light is with a PAR meter and then it will still differ around the tank in different positions and heights. Then alter the lighting height/positions to match a 'peak distribution'.

If like me you think that all this garble about lighting is pointless really and that a PAR meter is a bit of a rich man's toy (You only need it once per setup, get the light right and then put it back in the cabinet for a long time) then use the cheap PAR meter - Plants :lol:

If I were to move back to fluoro from the LEDs I currently use then I would move back to T8s on electronic ballasts which are what I currently use for my emersed setups.

When people come back at you with any scientific or mathematic 'facts' then take them at face value!!! Remember that all government scientific research studies in US and UK state very clearly that phosphate and nutrients that are from agricultural fertilisers that run off the fields CAUSE algae. Therefore this must be true after all they are pretty good scientists .

However we know this is wrong (or at least phrased incorrectly.) we actually add these same nutrients in without algae being CAUSED. However we know that algae does feed of those nutrients just as plants do. Algae needs to be triggered/caused before it can feed on the nutrients though.

We have large plantmass whilst the waterway authorities are constantly dredging the *****, ditches and waterways, clearing out plantmass and then getting algae blooms. So we non scientists concur that if they left the waterways alone, let the plants grow, left the silts alone then algae wouldn't occur (in the quantities they do from disturbed sites) and the fertiliser CAUSE is therefore invalidated.

Apply the same to any suggestion about lighting. Science/Maths can indicate what could be the best way but this is hardly ever exact for our purposes  Better overall growth can often be less actual light supplied BUT distributed better.

AC


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## dawntwister (Sep 29, 2007)

Supercoley1 said:


> Cheap PAR meter - Plants :lol:


This is what this thread is about. Seeing how Hygro Sunset develops under different lights. Perhaps this will help others save money.

I tried dosing ferts flourish comprehensive and nitrogen daily with 40 watts of light. Also added natural charcoal to the substrate. Still Hygro Sunset would not turn pink. Thus started experimenting with different bulbs. Bought according to the K rating for it is the only parameter consistent with bulbs. I choose K rating around 65k since that is suppose to be near sunlight. I found the hard way that the spectrum's the bulbs actually have depends on the manufacture. For the Phillips daylight bulb 65k did not do much for my plants.

Two days after adding Life-Glo2 and Zoo Med super-daylight bulbs Hygro Sunset pink color is the brightest it has ever been. Life-Glo2 is the winner. When Zoo Med dies I will replace it with cheap aquarium light from Lowe's


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## Supercoley1 (May 28, 2007)

I think that daylight is actually 5500K (not sure but that is the pure white look where 6500K is a tinge green.)

Remember when going by K rating that the CRI is also important.

For example a cheap hardware light may be a 565 = 50-59% accurate to 6500K whereas a quality light (not always the case) may be a 965 = 90-99% accurate to 6500K.

If you want red plants to look red then mix a pink light in and they will suddenly look super red 

AC


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