Lighting Question?

[Firstman]

Hello all, have a lighting question for you. I didn't see a Lighting thread so I hope that the Plants section will work since it does pertain to plants. I have a 40 gallon newly planted tank with CO2. The light that I am using is a Current Dual Satellite w/ two 65w bulbs. One is a 6,700k/10,000k and the other is a 420nm/460nm Actinic. Do you know if the spectrum from the Actinic is good for freshwater plant growth? I have seen sites stating that they are good for Marine Coral growth and also for freshwater, but most reading material talks about the benefits for Marine. Do you think I should keep the Actinic or replace with another 6,700k/10,000k? Or get a 6,700k only? Any info or comments would be greatly appreciated. I don't want to buy another bulb when this one is still new (it came with the fixture) but will do what is best for the plants.

 

[Mr Bliss]

I'd love to hear a definite answer to this as well. Some say avoid high K lights, others say that plants don't care about the color temperature. Some also say that bluish light promotes algae, but I don't see that. I use 14,000K blue-white metal halide. Granted, the tank is only a couple of months old, but it has remained algae-free so far (aside from a little bit of thread algae coming and going after the substrate burped up some nutrients early on) with good plant growth.

 

[Colin_T]

Plants require red & blue light to grow. One encourages them to grow tall and the other makes them bushy.
Lights with a temperature or Kelvin (K) rating around 10,000K have plenty of blue in them. Lights with a temp of 3-5,000K have plenty of red in them.
Actinics and blue lights have a temp around 16 to 20,000K.
Blue light penetrates water more than red light, which is why many people use it for marine tanks. Some corals that are kept in aquaria come from deeper water where their main source of light is in the blue wave length. Freshwater plants however, generally come from shallow water, (less than 10ft deep). This means they get plenty of red light as well as blue light.
Natural sunlight is around 5,700K. For freshwater plant tanks use lights that are between 5,000K & 10,000K.
10,000K globes will give a clear white light but it will have plenty of blue & red wavelengths in it for the plants.

Algae generally grows from excess light and nutrients and not enough plants to utilise the stuff that is present.

 

[Dave Spencer]

Plants require red & blue light to grow. One encourages them to grow tall and the other makes them bushy.

Where do you get these statements from, Colin? This seems very simplistic and incorrect.

Dave.

 

[aaronnorth]

Algae generally grows from excess light and nutrients and not enough plants to utilise the stuff that is present.

Yes i have never read about the blue & red quote either?

Also excess nutrients dont cause algae, it is an imbalance in nutrients

 

[Colin_T]

Plants require red & blue light to grow. One encourages them to grow tall and the other makes them bushy.

Where do you get these statements from, Colin? This seems very simplistic and incorrect.
Dave.

Books that I have read over the years.
People like simple because it is easy to understand. If they want a detailed exacting explanation they can ask the same question in the scientific section. But here, most people want a simple easily understood answer.

Algae generally grows from excess light and nutrients and not enough plants to utilise the stuff that is present.

Yes i have never read about the blue & red quote either?
Also excess nutrients don’t cause algae, it is an imbalance in nutrients

An imbalance might mean there is an excess of one or two nutrients and an absence of others. But plants & algae grow more readily when there are lots of nutrients in the water compared to when there is very little nutrient in the water.

 

[andywg]

It seems amazing to me that planted peeps have never heard of plants absorbing from the red and the blue ends of the spectrum.

First off, consider how reflective light works. We see the colours that are not absorbed by an object. Put very simply; if it reflects almost all colours then it appears white, if it reflects none it appears black. Plant leaves appear green indicating it is absorbing light at the red and blue ends of the spectrum while reflecting the green in the middle.

According to Wikipedia Such a hypothesis was backed up by the work of Gross in 1991 which states:

In diethyl ether, chlorophyll a has approximate absorbance maxima of 430 nm and 662 nm, while chlorophyll b has approximate maxima of 453 nm and 642 nm.

The absorption peaks of Chlorophyll a are at 665 nm and 465 nm. Chlorophyll a fluoresces at 673 nm.

Those numbers would put the absorption of chlorophyll centred in the red and the blue areas.

 

[aaronnorth]

It seems amazing to me that planted peeps have never heard of plants absorbing from the red and the blue ends of the spectrum.

We never said that plants used blue & red parts of the spectrum, we said that we didnt know that blue & red made them bushy or tall

An imbalance might mean there is an excess of one or two nutrients and an absence of others.

Yes, that is what i said the first time - an imbalance of nutrients which causes algaes like green water algae blooms)

But plants & algae grow more readily when there are lots of nutrients in the water compared to when there is very little nutrient in the water

Algae grows more when there is less nutrients in the water column, take EI as an example, this smashes that quote, you overdose nutrients & this is an excellent way of combatting algae. Low nutrients cause algae, for example low NO3 causes BGA.

 

[Colin_T]

But plants & algae grow more readily when there are lots of nutrients in the water compared to when there is very little nutrient in the water

Algae grows more when there is less nutrients in the water column, take EI as an example, this smashes that quote, you overdose nutrients & this is an excellent way of combating algae. Low nutrients cause algae, for example low NO3 causes BGA.

I have to disagree with you Aaron. If you have two containers of distilled water and add some plant fertiliser to one of them. Then put both containers under a light, the container with the nutrients in will grow algae much sooner than the container with only distilled water.
The EI method uses the plants to keep the algae under control. Basically you force growth the plants and they out-compete the algae. When plants are growing well they produce a chemical that inhibits algal growth on them. If you get enough plants growing you get plenty of the hormone and it acts as a natural algicide thus reducing algal growth in the tank.
The faster the plants grow and the more leaves they have, the more light they use, thus reducing the light available to the algae.
Many algae are also susceptible to over fertilising. You can often kill algae (and higher plants) with excess nutrients. You provide so much food they grow extremely rapidly for a short time before they burn out and die. In terrestrial plants too much fertiliser will physically burn the roots or leaves of the plants, potentially killing them. Being a single celled organism, algae doesn't have the protection of bark or cellulose fibres and is more susceptible to high levels of fertiliser. It goes straight through the cell walls and damages them.

Blue green algae generally grows in water with high levels of nutrients. In newly set up marine tanks a red form of it grows due to the unstable environmental conditions that are present during the first few months. In natural waterways, (rivers, creeks, streams, etc) it grows from a build up of nutrients and low oxygen levels, which are often associated with low water movement.

 

[andywg]

We never said that plants used blue & red parts of the spectrum, we said that we didnt know that blue & red made them bushy or tall

You were not quite so clear cut in your earlier posts, however, I accept an error in comprehension was performed by me and shall, as such, provide support for Colin's statement regarding blue and red light's affect on plants.

First off one might look into the writings in:

Blue Light Inhibits Stem Elongation of Chrysanthemum by H. Shimizu, Z. Ma, S. Tazawa, M. Douzono, E.S. Runkle and R.D. Heins appearing in ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture

This article found that compared to the NI delivered by fluorescent lamps (the control samples), the blue LED NI inhibited internode elongation by approximately 60%. The inhibitory effect of blue light occurred during the night interruption and in the subsequent light period. These results indicate that blue light could be used to inhibit extension growth and therefore could reduce the application of plant growth retarding chemicals.

Also, consider:

Effect of red- and blue-light-emitting diodes on growth and morphogenesis of grapes; Puspa Raj Poudel , Ikuo Kataoka and Ryosuke Mochioka, Plant Cell, Tissue and Organ Culture Volume 92, Number 2 (February, 2008) pp. 147-153 the abstract for which notes:

The effect of red- and blue-light-emitting diodes on shoot and root growth of Hybrid Franc grape, a rootstock cultivar, along with two other grape genotypes, Kadainou R-1 and Vitis ficifolia var. ganebu, were investigated in vitro. Plants cultured under red-light-emitting diodes produced the longest shoots with longer internodes for all genotypes. The chlorophyll content measured as SPAD value and leaf number per explant were highest on plants cultured under blue-light-emitting diodes in all the genotypes. Blue light was also responsible for a higher number of stomata in all the genotypes; however, there was no significant difference in size of stomata in all genotypes under the different light conditions tested. Different light-emitting diodes did not affect the rooting percentage of Hybrid Franc but red-light-emitting diodes gave a higher rooting percentage along with higher root numbers for the two other grape genotypes.

So from the above we can see that red light appears to make plants grow in longer stems meaning leaves are further away from each other but the plant will be taller whereas blue light prevents such long stem growth causing the leaves to grow closer together and appear bushy. The simplified way to look at this is to consider that bluer light will result in shorter bushier plants while red light will provide thinner taller plants after a given amount of time (all other things being equal).

 

[Dave Spencer]

Coiln, you may simplify things, but saying blue and red light cause tallness and bushiness is wrong.

Excess nutrients do not cause algae, otherwise high light tanks will not work. Have you grown algae in water at a purity of 0.02mS/cm? I have. Have you dosed ferts to excess in an algae suppressed tank? I have and couldn`t induce algae.

Andywg, when it comes to lighting a planted tank I suggest people follow the two considerations of:

Intensity: the amount of light which will determine growth rates, fert regimes and maintenance levels.

Colour rendition: buy tubes that look good to the eye, which generally means buying one with a decent green spike.

Aquatic plants grow in an environment of ever changing light quality due to seasons, time of day, shade, water discolouration etc. so it doesn`t seem reasonable to think that they only utilise certain parts of the spectrum. Plants contain other pigments besides Chlorophyll a and b, such as carotenoids, flavonoids and xantophylls. These allow plants to utilise other parts of the spectrum, and their quantities will vary with the quality of light available to the plants.

Work has been carried out by V A Helson at the Canadian Department of Agriculture and R W Ashley and J A Bartok, testing cool white lamps against plant specific lamps to measure relative rates of growth. No measurable difference in growth rates was observed.

I recommend people buy cheap lights with a good CRI, and let the plant pigments do the rest. I use cheapo £3 daylight tubes under which I can grow some pretty demanding plants.

Dave.

 

[Dave Spencer]

Good post, Andy. You read too much. I wonder how relevant this study is to aquatic plants, where light quality can be hugely variable throughout the photoperiod. Plants seem to be very adaptable and opportunistic to what light is available to them. There is actually no such thing as a high light plant in aquatics because they can all adapt to low light and various spectrum shifts. This the area where they are most efficient, as opposed to when I grow them in high light and become nutrient wasteful. The big problem is that algae is even more opportunistic and quicker to respond to variations that will have an affect on plant growth rates.

I do know that actinics are used successfully in planted tanks, but they are certainly not to my taste.

Colin, I think you are alluding to allelopathy. If so, this is a theory that carries less and less weight,and is refuted byOle pedersenof Tropica.

Dave.

 

[aaronnorth]

Blue green algae generally grows in water with high levels of nutrients. In newly set up marine tanks a red form of it grows due to the unstable environmental conditions that are present during the first few months. In natural waterways, (rivers, creeks, streams, etc) it grows from a build up of nutrients and low oxygen levels, which are often associated with low water movement

I am not goignt o go on about marines because i know zero about them. Plus i think it is irrelevant due to the different water conditions that maaines tanks have/ need.

BGA is often caused by very low nitrates. It is fairly common to have it growing in the substrate against the front glass from where it can spread. Sometimes it appears with new setups that have had light and ammonia present at some point. Dirty substrates and filters may also bring it on. Bad water circulation is another possible cause.

How come then when doisng EI or a similar method like PMDD why is that BGA never grows? I know someone on another forum who doses 3x EI!!


Excess nutrients dont cause algae ever, only an imbalance does (i nwhich there may be to much of one nutrient and not enough of another, but this isnt classed as too much of that certain nutrient)

Thanks for the info Andy, but i still think that accordong to colins statement -

Plants require red & blue light to grow

you do not need red & blue. I bet if you got a plant, and used a light which was just green that it would still grow perfectly normal as long as it had sufficent light & nutrients.