Lighting in Planted Tank

Dedicated to Planted aquarium specific Lights, Substrate and other equipements
Forum rules
Before you start posting in this forum, will suggest you to go through the forum rules
HERE

Re: Lighting in Planted Tank

Postby joyban » Wed May 02, 2012 10:42 am

Light Intensity in an aquarium:-

The following parameters do apply to light physical properties as it travels from the source to water and into it, primarily which are as:-

· A photon of wavelength 700nm from the red end of the spectrum will have less energy from a photon at 400nm from the blue end of the spectrum. where energy = (1988/ λ) X 10-19 Joules,where λ = wavelength

· Hence at 400nm the energy of a photon is 233.33% more than the energy of a photon at 700nm.(energy at 400nm = (1988/400) x 10-19 Joules = 4.97 x10-19 J and at 700nm it is 2.84 x10-19 J)

· Light travels at a velocity equal to the velocity of light in a vacuum divided by the index of refraction (n), which is typically for water n = 1.33. Water 100'C 1.31; Water 20'C =1.33335 & Water 35'C = 1.33157

· Hence the velocity in water is about 2.25x10^8 m/s. Because light travels slower in water than in air, some light is reflected at the water surface. For light shining straight down on the water, the reflectivity is (n - 1)2 / (n + 1)2.

· For freshwater, the reflectivity is 0.02 = 2% at zenith angle of incidence between 0 to 20 degrees and then it remains low increasing rapidly after 50 degrees, to 89.6% reflectance at 89 degrees of incidence angle.


See Chart below:-

Zenith Angle Of Incidence Degrees Reflectance %


0 deg 2.0% 50 deg 3.3%
5 deg 2.0% 55 deg 4.3%
10 deg 2.0% 60 deg 5.9%
15 deg 2.0% 65 deg 8.6%
20 deg 2.0% 70 deg 13.3%
25 deg 2.1% 75 deg 21.1%
30 deg 2.1% 80 deg 34.7%
35 deg 2.2% 85 deg 58.3%
40 deg 2.4% 87.5 deg 76.1%
45 deg 2.8% 89 deg 89.6%

Image

Image

Reflectance of Unpolarized Light from a flat Water Surface assuming that the water has a refractive index of 1.33See – Fresnel’s Equation
Hence most sunlight reaching the water surface is transmitted into the water, little is reflected. This means that light incident on the water surface in the aquarium is mostly absorbed below the water surface.

At this moment on water surface and just below the water surface light or photons are lost by absorption and scattering out of path and Gain by scattering into path. Also there is a factor of refraction and reflection of light at air –water boundary as shown below :-


Image




Refraction and reflection of light at air-water boundary. (A) A light beam incident from above is refracted downwards within the water: a small part of the beam is reflected upwards at the surface. (B) A light beam incident from below at a nadir angle of 40° is refracted away from the vertical as it passes through into the air: a small part of the beam is reflected downwards again at the water-air boundary. (C) A light beam incident from below at a nadir angle greater than 49° undergoes complete internal reflection at the water-air boundary.
Ref:- (Source Page 45 Light and Photosynthesis in Aquatic Ecosystems)

Also how much light is reflected or refracted depends on the wind speed and disturbance of the water surface by wind , in case of a aquarium it can be attributed to water movement on the surface due to Air Pumps, CO2 diffuser or power heads.

The light absorbing components of the aquatic system are :-

· The Water Itself
· Dissolved Yellow Pigments
· The Photosynthetic biota
· Inanimate Particle matter

Water:-
Water though it appears colorless in small quantities is blue in colour and it absorbs light more in the region from 550nm and above quiet significantly in the red region. It has been found out that about 35% of incident light at 680nm is absorbed at 1 meter depth of water or 1 meter thickness of water. So if we were to refer the absorption Coefficients derived from the published attenuation coefficient Morel & Prieur 1977 you would see that at 380nm the value is as 0.023 , 400nm = 0.018 ; 450nm = 0.015; 500nm = 0.026; 550nm = 0.064 ; 600nm = 0.157; 630nm = 0.310; 650nm = 0.350 ; 670nm = 0.430; 680nm = 0.450; 690nm = 0.500 and at 700nm it is 0.650;
At 740nm ,760nm and at 800nm the values are as 2.38, 2.55 & 2.07


Hence Blue light is absorbed least, red light is absorbed most strongly.

Attenuation per unit distance is proportional to the radiance or the irradiance of light where x is the distance along beam, c is an attenuation coefficient and I is irradiance.

dI/dx = -cI

Image

Figure Absorption coefficient for pure water as a function of wavelength λ of the radiation. Redrawn from Morel (1974)

If the absorption coefficient is constant, the light intensity decreases exponentially with distance.

I2 = I1 exp(-cx)

where I1 is the original radiance or irradiance of light, and I2 is the radiance or irradiance of light after absorption.

Actually the contribution of water itself to the attenuation of PAR by absorption of quanta is important only above about 500nm, and where we use artificial light which have more spectrum in blue and blue green range rather than at red, yellow - red range ( a good full spectrum light may have a good ratio of red : blue though the light may be towards or around 3500K to 4000K) would mean that more red light or photons are lost compared to the blue as they travel downwards with in water, now how much of this loss is significant to an aquarium where the water depth may not be more than 18 to 24 inches ( 1 meter = 39.37 inches) is a question one has to measure and check ; hypothetically more blue light reaches the plants than red as we go downwards the depth of water from surface.

Humic, Tanin etc:-
From the point of view of photosynthesis water soluble humic substance impart yellow colour in water and this leads to absorption of light particularly at the blue end of the spectrum. Yellow material of the humic type can also be generated by decomposition of plant mater with in the water body.

So due to tanin, humic acid in water Blue light is absorbed more towards the 400nm to 550nm region and much less at and beyond (drops significantly) at 600nm region.

Particles:-
The inanimate particulate matter in water and their typical concentration does not absorb light strongly but scatters quiet intensely but studies have shown that absorption is low or absent at the red end of the spectrum and rises steadily as wavelength decreases into the blue end of the spectrum.

The Photosynthetic biota:-
The Absorption of Light by the photosynthetic pigments – chlorophylls, carotenoids , biliproteins etc contributes to the attenuation of PAR with depth. Specific absorption coefficient corresponding to 1mg of chorophyll a per unit area of 1 meter cube is as :-

At 400nm = 0.017, 450nm = 0.024 ; 500nm = 0.018 ; 550nm = 0.011; 600nm =0.007 650nm= 0.014 & at 700nm= 0.003 so it is a maximum around 440nm almost touching 0.025 and then dipping at around 575nm and again peaking around 670nm at 0.018 almost like the photosynthesis action spectrum curve.

Hence as light travels through the depth of water there is significant amount of light loss due to various factors like water depth itself, tanain humic acis, other particles , dust, and then the chlorophyll from algae & plants itself, hence a combination of these contribute to light loss in water or loss of photons in water.

Scattering of Light within the aquatic medium also contributes towards the availability of photons for photosynthesis. Many of the photons undergo scattering one or more times before they are absorbed . Scattering does not remove the photon but the photons have to travel more in a zig zag path as they get scattered and this increases the total path length traveled by them which may result in capture of the phonon by one of the components of the absorbent medium (water) as mentioned above. In addition some photons are scattered back in upward direction thus the effect of scattering is directly related to the light or photon intensity and the vertical attunation of light in water due to scattering of light by density fluctuation or by particle scattering.

Scattering of pure water is of the density fluctuation type and varies with wave length. Experimentally scattering is found to vary in accordance with 1/λ4.32 . The scattering coefficient of natural waters are invariably much higher than those of pure water. See table below:-

wavelength scattering coefficient/ meter


Pure Water

400nm= 0.058
450nm= 0.0035
500nm= 0.0022
550nm= 0.0015
600nm= 0.0011


Pure Sea Water

450nm= 0.0045
500nm= 0.0019

Marine Water

Atlantic Ocean - Sargasso Sea
440nm= 0.04
633nm= 0.023

Pacafic Ocean - Galapagos Is.
440nm= 0.08
655nm= 0.07

Fresh Water- River - Irondequoit Bay Ontario
400-700nm= 1.9-5.0

Perry - Tasmania
400-700nm= 0.27

Gulungul - Myrray Darling System
400-700nm= 5.7


Fresh Water- Lakes - Rotokakahi
400-700nm = 1.5
400-700nm = 2.1
400-700nm = 3.1

(Source Page 101 Light and Photosynthesis in Aquatic Ecosystems by by John T.O. Kirk )


Hence
Attenuation of light in the water column – due to absorption and scattering

Transmittance (amount of light left) = Iz/ I0 x 100
where I = irradiance,
I0 = irradiance just below surface
Iz = irrad. at depth z

Absorbency [100 x (I0 - Iz)]/I0

Image

Figure Left: Attenuation of daylight in the ocean in % per meter as a function of wavelength.
I: extremely pure ocean water; II: turbid tropical-subtropical water; III: mid-latitude water; 1-9: coastal waters of increasing turbidity. Incidence angle is 90° for the first three cases, 45° for the other cases. Right: Percentage of 465nm light reaching indicated depths for the same types of water. From Jerlov (1976).

Image
Light Loss in Water

Image
Light Absorption by wavelength

Image
Light Attenuation and PPFD Attenuation with depth

Natural Light Attenuation In Aquarium
Image

Attenuation equation
Iz = I0 e - kz
where e = natural logarithm
k = attenuation coefficient (extinction coefficient ref- Wetzel)
characteristic for each water body and each wavelength
often converted to a linear plot by taking the log of both sides:
ln Iz = ln I0 – kz


Components of the attenuation/extinction coefficient

K_l = K_abs + K_ scattering
K = K_water + K_dissolved organics + K_particulates


K_water
- for pure water, absorption at long wavelengths dominates (>550 nm; red and IR)
- So, IR disappears in the top 1-2 m of most lakes
- Scattering at short wavelengths, <380 nm
- Pure water does not absorb UV (only scatters it)
- Dissolved salts do not increase attenuation


K_dissolved organics
- dissolved organics - humic and fulvic acids
- absorb strongly at short wavelengths -- blues and UV's (<500 nm)

K_particulates
- absorbs light evenly over the entire spectrum
- often the particulates are predominantly tripton and phytoplankton
-detritus may have higher absorbance at the blue end


Hence based on these transformation that Photons or light undergo while they travel from source to the plant leaves we should conduct experiments to measure the following:-

1. Measurement of PAR right at the Source
2. PAR Values as they change over with use of correct reflector
3. PAR at Tank bottom with out any water, only AIR
4. PAR at water surface & just below with out any water movement
5. PAR at water surface & just below with water movement – diffusers, power heads , filters etc.
6. PAR at various levels or depth in water may be with a 1 inch gap.
7. PAR at various plant canopy level ( Tall / Medium/ Low height Plants)
8. PAR at Substrate
9. PAR at different Water types – Clear Water; Black water etc

This will help is collate the data collected based on studies as described above and then actual measurements results which this experiment will lead to better use (efficiency & economical) of artificial light for aquaria.

Though this article explains the physical property of light as it travels from an artificial source like a fluorescent or a MH light light in an aquarium through Air into Water and ultimately reaches the plant leaves ( also same principle is applicable to natural light), Actual photosynthesis which a plant may undergo depends on many more factors but this information will at least help to understand how much PAR a particular bulb or alight source may contribute at water surface and at the substrate and over plant canopies and how & Why the PAR values change as they travel with in water. Thus we might be able to predict to some extent the right amount of light an aquarium may need based on these principals. This also in general states that Watts per gallon rule may not significantly contribute to a scale of measurement or a baseline as light under goes significant changes as it travels through water and plants adopt differently to the available light over a period of time provided that the other parameters of CO2 and Fertilization are kept at optimum level for plant growth. Significantly it has been found that Light is not the limiting factor for plant growth (just as our eyes can adjust to bright and dull light) as much as to CO2 or the available nutrients in water.

An interesting reading may be this article on effect of light on growth and photosynthesis of Egeria najas at :-
http://www.scielo.br/pdf/babt/v46n2/16288.pdf

Adaptation to Low Light Levels by Hydrilla..
http://www.apms.org/japm/vol15/v15p32.pdf

To be Continued...
Last edited by joyban on Wed May 02, 2012 12:33 pm, edited 2 times in total.
joyban
Regular in KAC
Regular in KAC
 
Posts: 129
Joined: Wed Mar 21, 2012 8:46 am
Location: New Delhi
Has thanked: 0 time
Been thanked: 0 time

Share On:

Share on Facebook Facebook Share on Twitter Twitter Share on Orkut Orkut

Re: Lighting in Planted Tank

Postby joyban » Wed May 02, 2012 11:27 am

There is one other concept which has to be discussed:-

Photosystems:-

The light-dependent portion of photosynthesis is carried out by two consecutive photosystems (photosystem I and photosystem II) in the thylakoid membrane of the chloroplasts. The photosystems are driven by the excited chlorophyll molecules.

To begin photosynthesis, the chlorophyll molecule in photosystem II is excited by sunlight and the energy produced helps to break down a water molecule (H2O) into ½O2 (with electrons removed) and 2H+. The removed electrons are excited by the light energy. When the electrons prepare to come to their rest state, they go through an oxidative phosphorylation process and produces an ATP molecule.

As the electrons are coming to a resting state, they are excited again in photosystem I and raised to a even higher energy state. The excited electrons are then used to produce NADP+ + H+. The highly energetic NADPH molecule is then fed into the Calvin Cycle to conduct carbon fixation.

Image

Image


Image

Thinking of this system, you can see that an electron is excited by light energy absorption in a P680 chlorophyll, a reaction center pigment in PSII. This electron is passed through an electron transfer to PSI. The electron lost is replaced by the photolysis of water. This reaction is sometimes called the Hill reaction in honor of Robin Hill who studied it.

Photolysis of water is the source of the oxygen produced in photosynthesis.

The electron that left PSII and passed through the electron transfer system replaces an electron that is lost by PSI after it is excited by 700 nm light energy.

This electron is ultimately trapped with an accompanying proton onto NADP+, a high-energy vitamin B molecule.

You should also notice that PSI is not a strong enough oxidant to draw electrons from photolysis of water, and that the energized PSII is not a strong enough reductant to donate electrons to NADP+

Thus, both photosystems are needed to both oxidize water and to reduce NADP+...this explains why Emerson observed the red/far-red enhancement effect as had been mentioned earlier...

This is only to emphasis on the Point that both Red and Blue Spectrum of Light contributes to Photosynthesis...
joyban
Regular in KAC
Regular in KAC
 
Posts: 129
Joined: Wed Mar 21, 2012 8:46 am
Location: New Delhi
Has thanked: 0 time
Been thanked: 0 time

Re: Lighting in Planted Tank

Postby Tirtha » Wed May 02, 2012 12:16 pm

After a 7 years of constant nagging when I see these write up from Sujoy da, I feel successful.
Regards,
Tirtha

A Bad Attitude is like a Flat Tyre. You cannot go anywhere until you change it.
User avatar
Tirtha
Admin
Admin
 
Posts: 4251
Images: 20
Joined: Thu Mar 08, 2012 11:27 am
Location: Hyderabad
Has thanked: 12 times
Been thanked: 73 times

Re: Lighting in Planted Tank

Postby joyban » Wed May 02, 2012 12:22 pm

Synopsis :-

Factors Influencing Photosynthesis:-

Blackman’s law of limiting factors

Blackman (1905) proposed the law of limiting factors according to which when process is conditioned to its rapidity by a number of factors, the rate of process In limited by the pace of the slowest factor. Blackman’s law of limiting factor is modification of Leibig’s law of minimum, ( Ref:- http://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum) which states that rate of process controlled by several factors is only as rapid as the slowest factor permits. Theory of three cardinal points was given by Sachs in 1860. According to this concept, There is minimum, optimum and maximum for each factor For every factor, there is a minimum value when no photosynthesis occurs, an optimum value showing highest rate and a maximum value,above which photosynthesis fails to take place.

External factors

1. Light

In photosynthesis light is converted to chemical energy in the food formed. It can be studied under three headings (i) Light intensity (ii) Light quality and (iii) Light duration (i)

(i) Light intensity. Light intensity required to get the optimum value differs with different species. Usually with increase in light intensity, increase in rate is noticed Clouds, fog, dust and atmospheric humidity reduce the intensity. Submerged aquatic plants also get less light intensity. At very high light intensity the cells exhibit photo-oxidation by the process of solarization and if continues for few hours, the photosynthetic apparatus is destroyed. Plants which are able to grow in shades are called as sciophytes while those growing in intense light are called heliophytes. It also affects the opening and closing of stomata thereby affecting the gaseous exchange mostly in terrestrial plants. The value of light saturation at which further increase is not accompanied by an increase in CO2 uptake is called light saturation point.

1.Light

(ii) Light quality. Blue and red light of the spectrum is said to be the best light for the photosynthesis. The green light has inhibitory effect.
(iii) Light duration. Plants getting average light of 10-12 hours a day show higher rate of photosynthesis.

2. Carbon dioxide

Carbon dioxide is present in low concentration and forms about 0.032% of the total atmosphere. Increased concentration of CO2 with other factors not becoming limiting rate of the process enhances. However, very high concentration of CO2 becomes toxic to the plants.

Aquatic plants usually have access two sources of inorganic carbon: carbon dioxide (CO2) and bicarbonate (HCO3-). Most aquatic plants prefer CO2 rather than bicarbonate because it can be taken up from the surroundings without any energetic expenses and many aquatic plants are not able to directly utilise bicarbonate in the photosynthesis. Like a Light compensation point there is a CO2 compensation point as a point where CO2 concentrations below this point result in a negative net photosynthesis whereas concentrations above this point result in a positive net photosynthesis. One of the curves has a CO2 point of zero. This illustrates the bicarbonate user, which can continue to carry out positive photosynthesis even at zero CO2 because it can use bicarbonate as a source of inorganic carbon.

Image

In nature, the concentration of CO2 is often larger in water than in air but in spite of that the actual availability to the aquatic plant is lower. This is because of the slow movement of gasses in water where the diffusion is 10,000 times lower in water than in air. Hence, although the concentration of CO2 in many streams and rivers may be larger than in air, the slow movement of gasses in water eventually leads to CO2 limitation of aquatic plant growth. The thin leaves typical of submerged plants greatly alleviate the CO2 limitation. This is partly because thin leaves hold thinner boundary layers through which CO2 must diffuse and partly because once the CO2 enters the leaf it does not have to travel long before it is fixed to carbohydrates in the photosynthesis. Of much more importance is the ability of the plant to up- or down-regulate the different pools of enzymes (fx Rubisco and Pepcarboxylase) that take part in the carbon fixation. At low CO2 availability, the plant may invest more energy in enzymes, which help in process of CO2 uptake or CO2 fixation and thereby alleviate the effect of carbon limitation. Some plants are also able to produce isoenzymes, which are enzymes with different chemical optima and so the affinity for CO2 may be changed to favour CO2 uptake. It is unclear how important isoenzymes are in the process of CO2 uptake and in the scientific literature isoenzymes are often associated with temperature acclimatisation in plants.

The ecological implications of interactions between light and CO2 are obvious. If for example enhanced CO2 availability increases the light use efficiency it may allow aquatic plants to penetrate to greater depth where the light is scarce but concentrations of CO2 are higher due to remineralization in the sediment. High light availability may also allow aquatic plants to lower the CO2 compensation point (Maberly 1983, Maberly 1985). This may be particular advantageous for mat-forming photoautotrophs in shallow water. In such systems, the light is often abundant whereas concentrations of CO2 inside the mat are low due to low intra-mat water exchange. Here, the interactions between light and CO2 may allow the photosynthesising organisms to extract CO2 more efficiently as a result of a lowered CO2 compensation point.

Let see how CO2 and Light Energy are dependent on each other for the process of Photosynthesis:-

At low light and low CO2 there is not much energy to play around with for up or down-regulation of the pools of Chlorophyll or enzymes. If we then add a little more CO2 to the system the plant can afford to invest less energy and resources in CO2 uptake and that leaves more energy for optimising the light utilisation - more Chlorophyll can be produced without fatal consequences for the energy budget.

Hence, although we have not raised the light, the plant can now utilise the available light more efficiently. Exactly the same explanation can be used to explain why increased light can stimulate growth even at very low CO2 concentrations. With more light available, less investment in the light utilisation system is necessary and the free energy can be invested into a more efficient CO2 uptake system so that the CO2, which is present in the water, can be more efficiently extracted.

3. Water:-

Attenuation, Reflection and Refraction, Absorption of Light in Water and with water depth

- for pure water, absorption at long wavelengths dominates (>550 nm; red and IR)
- So, IR disappears in the top 1-2 m of most lakes
- Scattering at short wavelengths, <380 nm
- Pure water does not absorb UV (only scatters it)
- Dissolved salts do not increase attenuation

Dissolved organics in water
- dissolved organics - humic and fulvic acids
- absorb strongly at short wavelengths -- blues and UV's (<500 nm)

Dissolved particulates in water
- absorbs light evenly over the entire spectrum
- often the particulates are predominantly tripton and phytoplankton
-detritus may have higher absorbance at the blue end


4. Temperature

The optimum temperature for photosynthesis is 20 to 35°C. If the temperature is increased too high, the rate of photosynthesis is also reduced by time factor which is due to denaturation of enzymes involved in the process. Photosynthesis occurs in conifers at high altitudes at -35°C. Some algae in hot springs can undergo photosynthesis even at 75°C.

5. Oxygen

Excess of O2 may become inhibitory for the process. Enhanced supply of O2 increases the rate of respiration simultaneously decreasing the rate of photosynthesis by the common intermediate substances. The concentration of oxygen in the atmosphere is about 21% by volume and it seldom fluctuates. An increase in oxygen concentration decreases photosynthesis and the phenomenon is called Warburg effect. The explanation of this problem lies in the phenomenon of photorespiration. Oxygen may compete with CO2 for hydrogen and may be reduced in place of CO2

6. Osmotic relations

Availability of water is affected indirectly with respect to osmotic relations of the plants. Internal factors

1. Protoplasmic factors: There is some unknown protoplasmic factor which affects the rate of photosynthesis. It takes some time to initiate the process in seedlings even if the chlorophyll has appeared. Same is true, if the plant is shifted to light from prolonged darkness.

2. Chlorophyll contents: Quantity of chlorophyll seems to affect the process. In variegated leaves and green leaves, assimilation per unit leaf area has been found to be the same provided other factors are not limiting. The amount of CO2 fixed by a gram chlorophyll in an hour is called as photosynthetic number or assimilation number.

3. Accumulation of products: Accumulation of photosynthetic products, if not consumed or translocated results in stoppage of process gradually.

4. Structure of leaves: Characters like structure, position and distribution of stomata, intercellular spaces, vascular tissues have been noticed to affect the process directly.

One may ask how we can use all the above information in the plant aquarium hobby! Although all the individual resources are difficult to control perfectly, we should be able to determine how much light, how much CO2 and how much nutrients in the form of nitrogen, phosphorus, iron and micronutrients we would like to offer our plants. It is often a much more difficult and expensive task to provide adequate light over the plant aquarium. Both fluorescent light and highpressure lamps may produce sufficient light if supplied with effective reflectors but in deep aquaria (more than 50 cm) is very difficult to offer enough light to small light demanding foreground plants. Based on experiments, it has been suggest commencing CO2 addition before any other action is taken! We believe that even at very modest light intensities you will experience a conspicuous change in plant performance in your aquarium. The exact amount CO2 may always be discussed but if you do not have very sensitive fishes in your fish stock, concentrations from 25 and up to 50 mg/l will only improve plant growth. You will probably see that plants, which were barely able to survive before now, thrive in the presence of CO2.

This is because as we said earlier If we then add a little more CO2 to the system the plant can afford to invest less energy and resources in CO2 uptake and that leaves more energy for optimising the light utilisation - more Chlorophyll can be produced without fatal consequences for the energy budget. Hence, although we have not raised the light, the plant can now utilise the available light more efficiently.

We shall not subsequently see how the Artificial Light Parameters allow us to calculate a PAR Value for the Lamp....

To be Continued...
joyban
Regular in KAC
Regular in KAC
 
Posts: 129
Joined: Wed Mar 21, 2012 8:46 am
Location: New Delhi
Has thanked: 0 time
Been thanked: 0 time

Re: Lighting in Planted Tank

Postby joyban » Wed May 02, 2012 12:48 pm

Quick Recall:-

1. Light is Required for Photosynthesis, light intensity plays an important part. Low Light may result in negative photosynthesis, Medium Light may result in adequate photosynthesis, and High Light may mean good Photosynthesis but can also cause excessive heat and cause the plants to be over exposed to Light causing other problems including effect of over exposure & burns.

2. Where light is a limiting factor like in an aquarium adding CO2 helps as at higher concentration of CO2 light is not the limiting factor.

3. Blue Light as well as Red Light is required for Photosynthesis and generally Green Light is reflected.

4. While Light travels through water it is reflected, refracted and often Attenuated and Absorbed, Blue Light Least and Red Light Most.

5. The ultimate light intensity falling on plant leaves surface after from a artificial or natural light source is far less than the original intensity. Some of it is lost due to refraction in air ( due to Air particles), some is lost at Air Water boundary due to reflection, refraction. Water movement at surface, clarity vs dark water ( due to tannin etc), particles etc also contributes to loss of light. What is left after all this is what reaches the leaves surface enough to start the process of photosynthesis above the Light compensation point, ( LCP is different for different plants).

6. Photo system I & II both uses Blue and Red Light for Photosynthesis.

To be Continued...
joyban
Regular in KAC
Regular in KAC
 
Posts: 129
Joined: Wed Mar 21, 2012 8:46 am
Location: New Delhi
Has thanked: 0 time
Been thanked: 0 time

Re: Lighting in Planted Tank

Postby joyban » Wed May 02, 2012 1:16 pm

Now lets us look at the most commonly used artificial source of Light in our aquarium systems:-

1. Incandescent bulbs
2. Fluorescent bulbs
3. High-Intensity Discharge (HID)
4. Light Emitting Diodes (LEDs)


INCANDESCENT
Incandescent bulbs produce light when an electric current passes through a filament and causes it to glow. Because they are less energy efficient than other light sources, they are best used for task lighting that demands high levels of brightness.

The types of incandescent bulbs available include:

General service incandescent bulbs are the inexpensive, readily available light bulbs that most of us think about when we hear "light bulb." They produce a warm, yellow-white light that is emitted in all directions and are available in either a clear or frosted finish.

Reflectorized incandescent bulbs have a reflective coating inside the bulb that directs the light in one direction rather than all around.
Reflector bulbs put approximately double the amount of light on the subject compared to General Service of same wattage.

Parabolic Reflector (PAR) bulbs control light more precisely. They produce about four times the light of General Service (A). Weatherproof casing makes them suitable for outdoor spot and flood fixtures.

Tungsten-halogen incandescent bulbs produce a brighter and whiter light than other incandescent bulbs. They also have a longer life and provide more light per watt than standard incandescent bulbs, making them a more efficient choice. Halogen bulbs are available in two types: line voltage (220 Volts) and low voltage (12 volt).

Xenon rigid-loop, festoon and wedge base bulbs have a white light similar to that of halogen but have a much longer life rating (some up to 20,000 hours, much like fluorescent) and operate at lower temperatures than halogen.

More information read:- http://www.americanlightingassoc.com/Li ... Bulbs.aspx

Image

FLUORESCENT

Fluorescent bulbs produce light when an electric arc passes between cathodes to excite mercury and other gases producing radiant energy, which is then converted to visible light by a phosphor coating.

They use 1/5 to 1/3 as much electricity as incandescents with comparable lumen ratings and last up to 20 times longer.Because fluorescent
bulbs contain mercury, it is important to dispose of them properly.

Example such as T12, T8 and T5 Lamps

Compact Fluorescent Lamps (CFLs) are small fluorescent bulbs that can be used in most types of lighting fixtures. They are of two type Integrated and Non Integrated, where the Integrated one means that the starter circuit is with the Lamp (build in) and non Integrated are where they need an external starter circuit.

Image

Image

HIGH-INTENSITY DISCHARGE

High-Intensity Discharge (HID) bulbs produce light when an arc passes between cathodes in a pressurized tube, causing metallic additives to vaporize. They have long lives and are extremely energy efficient, but - with the exception of metal halides - they do not produce pleasing light colors.

There are four types of HIDs:

Metal Halide - Mostly used in Aquariums
High-Pressure Sodium
Low-Pressure Sodium
Mercury Vapor

Image

LED:-

Light Emitting Diodes (LEDs) produce light when voltage is applied to negatively charged semiconductors, causing electrons to combine and create a unit of light (photon). In simpler terms, an LED is a chemical chip embedded in a plastic capsule. Because they are small, several LEDs are sometimes combined to produce a single light bulb.

LED lighting in general is more efficient and longer lasting than any other type of light source, and it is being developed for more and more applications and can be controlled by electronic circuits and even computerized systems.

Image

Different Light Colour from LED
Image

Exact Light Colours from LED ( See the advantage to use a particular light color for Photosynthesis ) -To be discussed in details later

Image

Also the Same LED can be Programmed to produce different intensity and colour of light and can be controlled by a microprocessor

See the Video Below as an example...

[youtube]http://www.youtube.com/watch?v=y0FkGH2c_Tw[/youtube]


To be Continued....
joyban
Regular in KAC
Regular in KAC
 
Posts: 129
Joined: Wed Mar 21, 2012 8:46 am
Location: New Delhi
Has thanked: 0 time
Been thanked: 0 time

Re: Lighting in Planted Tank

Postby Achintya » Fri May 04, 2012 5:58 pm

:o :shock: OMG :shock: .are ou a man or a super human?nowhere in any forums i have ever seen posts like these.we should be proud enough that our forum is honoured by this great sujoy da..
The Best Revenge is Massive Success
User avatar
Achintya
KAC Senior Member
KAC Senior Member
 
Posts: 4356
Images: 11
Joined: Wed Mar 21, 2012 9:40 am
Location: Kolkata
Has thanked: 1 time
Been thanked: 10 times

Re: Lighting in Planted Tank

Postby krish.saha007 » Wed Jun 27, 2012 9:18 am

which light is needed for a 2 feet aquarium to turn into a planted aquarium ??? plz tell me the brand ??? where to get and price ??? :shock:
User avatar
krish.saha007
Regular in KAC
Regular in KAC
 
Posts: 234
Images: 0
Joined: Thu Jun 21, 2012 9:02 am
Has thanked: 0 time
Been thanked: 0 time

Re: Lighting in Planted Tank

Postby Rohan » Wed Jun 27, 2012 4:15 pm

'What is the height of your tank and which plants you want to grow?
User avatar
Rohan
Moderator
Moderator
 
Posts: 2700
Images: 1
Joined: Wed Mar 21, 2012 5:14 am
Has thanked: 0 time
Been thanked: 9 times

Re: Lighting in Planted Tank

Postby gangopadhyay » Wed Jun 27, 2012 4:40 pm

i am going to give my certificate of masters in botany back to CU
JAYOTTAM GANGULY
Taking stance: Second Innings
User avatar
gangopadhyay
Super Moderator
Super Moderator
 
Posts: 772
Images: 9
Joined: Mon Mar 12, 2012 3:40 pm
Has thanked: 4 times
Been thanked: 2 times

PreviousNext

Return to Lights & Other Equipments

Who is online

Users browsing this forum: No registered users and 2 guests