Lets talk about lighting an SPS tank

[ATJ]

Originally posted by cschumaker

Basic light theory says that objects that appear blue, for example, are reflecting the blue wavelength back and absorbing the other colors.

To be more accurate, an object may appear blue because it is reflecting MORE blue light than other wavelengths, but it does not mean that it is reflecting ALL blue light. It may also appear blue because of the light that is hitting it. For example, place a white piece of paper under actinic lighting and it will appear blue. Finally, something may appear blue due to a blue fluorescent pigment (although some researchers would argue that blue fluorescent pigments do not exist. A fluorescent pigment absorbs light at one wavelength and emits it at a longer wavelength.

I imagine this would mean that the coral is using the other colors of the spectrum for photosynthesis and not using the blue.

Absorption of light does not mean that the light is being used for photosynthesis, but rather it is not being reflected. Does a blue damsel use all wavelengths of light other than blue?

I do know there has been studies done on photosynthesis that shows that plants use red and yellow light for photosynthesis and not green.

I'm not aware of any studies that show that plants use yellow light to any great extent. Chlorophyll a, the most widely used photosynthetic pigment, has absorption peaks at around 450nm (right in the middle of blue) and 680nm (red), and these two colours are most used by photosynthetic organisms. Chlorophyll b] has peaks around 490nm (blue but heading towards green) and 650nm (red). Of course various accessory pigments can fill in the gaps between these peaks and allow plants and algae to utilise a wider spectrum of light.

Studies into the absorption and action spectra of isolated zooxanthellae show they absorb and utilise light from around 390nm to just under 700nm, which is pretty much the whole range of visible light. There are peaks around 450nm (blue) and 680nm (red) and so the zooxanthellae are more efficient at utilising light around these wavelengths. There are multiple strains of zooxanthellae found in corals both within coral species and between coral species. This may mean some variance in the absorption and action spectra between the zooxanthellae strains, but most evidence suggests that the differences affect the height of the peaks rather than the wavelengths of those peaks.

The symbiotic zooxanthellae, which are responsible for photosynthesis, are largely a golden brown colour. Any other colours seen in the coral come from pigments produced by the coral itself. The purpose of the pigments is not clearly understood but it has been suggested that many of them are photoprotective. If a blue pigment is photoprotective, it is likely that the pigment simply reduces the amount of blue light reaching the zooxanthellae to reduce the photosynthetic activity. This would be important for a coral in shallow water under full Sunlight where excess photosynthetic activity could be dangerous to the coral.

Another important point is that there are many different colours found in symbiotic corals but their zooxanthellae will largely have the same spectral requirements of light. The colours of the corals may have little or no influence on the light used by the zooxanthellae for photosynthesis, other than what is mentioned above. For example, I have seen blue and beige colour morphs of Pocillopora verrucosa sitting side by side under the exact same lighting conditions.

In summary:

a) I don't think you can make assumptions about the spectral requirements of a coral just from its apparent colour.
b) Blue light has been shown to be important in the photosynthesis of zooxanthellae.

 

[ATJ]

Originally posted by chevell

Yes they glow and there is a filament used in a mecury vapor vacume tube for halides.

There is no glowing filament in a metal halide lamps.

Second the only way to measure par accuratly in the spectrum that were using is with a very expensive par meter...very expensive as in 15 grand which by the way is not the one being used here.Do you have one of those meters and done experiments with it?

I am using an Apogee meter, the same as Joe (JB NY). See: Testing 250 watt MH lamps and Ballasts. Joe compared the meter to "very expensive par meter" (LiCor ) and found the margin of error was very small.

Third, there is no way to measure accuratly the par values between a halide and a VHO because they are completly different light sources both working on completly different theorys one still a glowing filament in a mecury vapor vacume tube the other glowing gas that is ignited and spread down the length of the bulb as in not the same "at all" as far as light intensity at a given point, you yourself admits to the point light source but then make the claim that i'm completly wrong???

It is impossible to measure the PAR of any light source - no matter how much the PAR meter costs. As already explained, PAR is a measure of the number of photons hitting an area over time. That has no meaning when talking about a light source. This is got nothing to do with the mechanisms used to produce the light but simply that PAR is not a measure of light output.

When you measure PAR with respect to corals, you are measuring how much light the coral receives. In an aquarium, corals placed at different distances from the exact same light source will receive different levels of PAR. This is a proven method for determining how much light a coral receives. It is irrelevant how the light was produced.

Not to mention there are no equal values in the wattage range of either bulb so no fair comparison can be made between the two bulbs.

At no point was I trying to compare two bulbs.

Stop trying to make an arguement with nothing to substanciate what your saying.

I was simply presenting basic concepts of physics and definitions. No substantiation is required as these are accepted concepts.

Might I suggest if you are going to imply that the photons emitted from one light source are somehow different from those emitted from a different type of light source, you are the one that need to substantiate your arguement as it goes against basic and widely held principles of physics.

You said yourself measuring at point light source directly under the bulb of a halide would not be a fair compairson yet you claim that when I said the same thing that I was wrong??

I don't believe I said anything of the sort. Please show where I made such a claim.

And if the statement by the guy with the par meter is so correct then why would those "former" metal halide guys say they tested their VHO'S on three diff "former" halide tanks and all three showed better color and growth with the VHO's, yet the guy with the meter showed the halides to be five times brighter or what ever it was. If the par meter showed them to be so much brighter then why the results from the guys who switched to the VHO's? Which would clearly indicate that the VHO's are actually brigher or better spectrum or what ever made them work better I don't know. That is just the opposite of what we might expect from the givin par reading we got a few thread pages ago.

You cannot use a PAR meter in isolation to say one light source is brighter than another, without specifying the conditions under which the measurements were taken. You can use a PAR meter to measure how much light is being received by a coral in an aquarium at a certain distance from a light source. You could use a PAR meter to determine if one light source provides more or less light to a coral in a tank to another by measuring the PAR at a coral under each of the light sources. This might suggest that one is brighter than the other, under those conditions.

There seems to be alot of variables here that no one seems to be able to explain, but for you to simply say that I was wrong seems just a bit presumptious and arguementive to me, and with no way to back up your claim your really outa line here.

Which claims are you referring to? I am more than happy to provide supporting data.

Oh and by the way you really should employ something to eat that algae in your tank.

I don't remember asking for your advice.

 

[ATJ]

Re: so not quite "completly wrong"

Re: so not quite "completly wrong"

Originally posted by chevell

I was indeed talking about the diff between the bulbs not weather the par is an acurate measurement and like I stated before the only par meter that can make an acurate measurement in our spectrums are the very exspensive ones that no one really seems to have.

It still appears that you do not understand PAR. As previously stated, PAR is the number of photons with wavelengths between 400 and 700 nm hitting an area over time. The spectra we use on our aquaria ARE in this range. PAR is PAR.

As stated above, Joe compare the inexpensive Apogee meter to an expensive LiCor sensor and it showed fairly similar results. The readings from the Apogee meters are more than accurate enough for hobby use.

And presently im seeing way more color in my tank on pieces that were in a so called 400 watt 20K tank and actually sun burning others and having to move them down near the bottom. This while only consuming 540 watts in a 150 gallon tank. NO way is any combo of 2 250 watt halides and some tiny actinic going to touch the brighness of my tank which would use the same wattage that i'm using now. So to me that whole par thing seems like a very inacurate way of measuring things.

Can you substantiate this claim? How does that provide any evidence that PAR - which has been proven to accurately measure how much light photosynthetic organisms receive - is a very inaccurate way of measuring things?

 

[Shouse94]

it's said that 1 MH covers a span of 2' X 2'.
NOw if you have a thank that's 36"x 15", not nearly as square shaped as the span of the MH optimum light. Does the extra 9" of light that the MH covers in a sense lights the outside of the tank?
In other words sense the tank isnt deep enough wouldnt the MH be a waste of light? or am i missing something here?

 

[ATJ]

Originally posted by Shouse94

it's said that 1 MH covers a span of 2' X 2'.

This is only a very approximate rule of thumb used for planning purposes. That is, when planning a tank to be lit by metal halide lights, plan for one light every 2'.

The actual coverage of a metal halide light will vary due to a number of factors including:

* orientation of the lamp;
* size, shape and design of the reflector;
* height of the lamp and reflector above the tank.

The coverage is not usually square, except maybe a vertically oriented lamp in a square reflector.

The height of the lamp and reflector has a large influence over the coverage of the lamp. The higher the lamp above the tank, the greater the coverage of the lamp, but with the greater coverage, the intensity of the light at any point in the tank will be decreased, as the same amount of light will be spread over a greater area. The closer the lamp is to the tank, the smaller the coverage will be, but the intensity of light received by the organisms in the tank will be higher. Note that if the lamp is placed closer to the surface of the water, the lamp must be adequately protected from splashes of water and a fan may be required to reduce heat transfer from the lamp to the water surface.

NOw if you have a thank that's 36"x 15", not nearly as square shaped as the span of the MH optimum light. Does the extra 9" of light that the MH covers in a sense lights the outside of the tank?
In other words sense the tank isnt deep enough wouldnt the MH be a waste of light? or am i missing something here?

If the combination of the orientation, reflector and height above the tank did in fact give you coverage of 2' by 2', then yes, you would have 9" of extra light that was missing the tank. You would also be short 12" of light along the length of the tank.

My recommendation for a tank that size would be to go with two metal halide lights configured to give around 18" by 15" coverage. Ensure the lamps are protected from splashing and you have sufficient cooling.

I have two 36x18x18" tanks, each lit by 2 150W MH lamps. These lamps give the tank excellent coverage.

 

[Shouse94]

thanks, big help.
do you not worry about the whole dawn/dusk factor?
what Spectrum bulbs do u use?

 

[ATJ]

While it would be great if you could accurately replicate the course of the Sun across the sky, including dawn and dusk, it doesn't matter a whole lot to the corals if you just have metal halide lamps that are on or off, as long as the corals receive sufficient PAR per day (intensity x duration). If you have fish in the tank, you may want to have dawn/dusk supplementation with fluorescent lamps just so they don't suddenly go from darkness to light and light to dark. The latter appears to be worse based on the observed behaviour of the fish - see what they do when there is a power outage. Also note that the metal halide lamps take up to 10 minutes to reach maximum output so the on cycle is generally not a problem, even for fish.

I run fluorescent lamps on my tanks for an hour or so before the metal halides come on and 2-3 hours after they go off.

I use 10000K BLV lamps and I am happy with the colour of these.

To demonstrate the difference the height of the fitting makes, I set up one of my spare 150W fittings over the floor of my fish room at different heights. I laid 3 cable ties to show a rough square 18" by 15" so you can see the effect for half your tank. The lamp was at 10", 8" and 6" from the floor. I also measured the PAR directly under the centre of the lamp on the floor (well about an inch off the floor as that is the height of the sensor). At 10", the PAR was 560 μE.m^-2.s^-1; at 8" it was 850 μE.m^-2.s^-1; and at 6" it was 1350 μE.m^-2.s^-1. So you can see the increase in intensity.

<b>Fitting at 10"</b>

<b>Fitting at 8"</b>

<b>Fitting at 6"</b>

 

[Shouse94]

that was awesome, my hats off to you.
I had no idea it seems that the MH doesnt light up nearly as much as i thought it would.
Is that 150w an HQI? Is that what you would reccomend?
If not do you know where i can get a dual 150w retro?
thanks for all the help

 

[LittleBlueGT]

Keep in mind the width of the beam of light that you are seeing is only at 6 or 8 inches. I doubt all of your corals are right at the surface of the water! The light will have better spread as you go lower in the tank water column.

 

[gjuarez3]

lets talk about lighting and sps tank or: How ATJ stole the forum and challenges everybody with terms half of us have never heard before.

J/K, great info ATJ

 

[JB NY]

You can also get the PAR ratings of MH lamps using pendants and other reflectors at Sanjay's lighting site. He tests them at a few distances as well.

 

[maxxII]

Wow, thats impressive stuff ATJ...
I knew about the INverse square law from photography, but didnt realize the effects were so dramatic within just a few inches. The intensity doubled within 4 inches!!

Nick

 

[cidory]

question for you lighting experts, I have a 50 Gal SPS tank recently converted to BB Starboard. it has 2 250 W XM MH and 150 VHO Actinic, 110 Watts of PC actinic, How long a photperiod should I be running , or is this trial and error, I currently run 10 hours a day with MH and 12 with Actinics, with the BB and the UV streilizer I have added this may be too much? Water clarity is so good I dont know there is water in the tank, any help ar advice is appreciated.

 

[Versus]

I think the largest problem now is the amount of choices we have , Way to many different variables to get any kind of "whats close to best" answer .

And alough the study
is nice , t5 are obviously missing and it shows the front of the tank . i use DE my self but i am sure SE would have more consistant "higher" numbers across the board than a de would , just because of the reflectors and having to use those stupid lenses.


ATJ how are babys made?

 

[ATJ]

Is that 150w an HQI? Is that what you would reccomend?
If not do you know where i can get a dual 150w retro?

It is my understanding that "HQI" is little more than a model prefix used by Osram for their metal halide lamps and that these lamps are really no different from other metal halide lamps.

The most important aspect of matching lamps to control gear is their running and starting voltages rather than whether they are "HQI" or not.

It is difficult me for recommend any brand over another because what is available here in Australia is quite different (and far more restricted) than what is available in the US. I have had great success with 150W double ended lamps but I am also having good success with normal output fluorescent tubes on normal output ballasts.

 

[ATJ]

You can also get the PAR ratings of MH lamps using pendants and other reflectors at Sanjay's lighting site. He tests them at a few distances as well.

In my opinion, "PAR ratings of MH lamps" can only be used as a very rough guide and only then for comparing one lamp to another. It is almost impossible to make inferences from the "ratings" as to how much light corals will be receiving at various locations in a tank.

"Ratings" for reflectors will be even less useful, unless they provide a map of the PAR over horizontal and vertical dimensions. If all that is provided is the PAR at a certain distance from the centre of the reflector, it will tell you very little as some reflectors may concentrate more light towards the middle and others may provide a better spread. The former would need to be raised higher to provide an even lighting, lowering the PAR received by corals whereas the latter could be placed lower.

 

[ATJ]

question for you lighting experts, I have a 50 Gal SPS tank recently converted to BB Starboard. it has 2 250 W XM MH and 150 VHO Actinic, 110 Watts of PC actinic, How long a photperiod should I be running , or is this trial and error, I currently run 10 hours a day with MH and 12 with Actinics, with the BB and the UV streilizer I have added this may be too much? Water clarity is so good I dont know there is water in the tank, any help ar advice is appreciated.

First of all, it should be noted that corals are extremely flexible with regards lighting and far more so than most hobbyists give them credit. They are found over a wide range of depths (and so lighting environments) and have various adaptations that allow them to make the most of the light they receive.

Second, it appears that (as a very broad generalisation) photoperiod is more important that PAR and that a minimum photoperiod is required to ensure that corals receive sufficient light, even if the lighting is very bright. (See: How much light is enough?). A coral will probably do better with less light for longer than with very high light for short periods.

Ultimately, however, there will be a lot of trial and error involved. In my opinion, the photoperiod should be at least 10 hours, but you could try less and see what impact it has on the growth of the corals. Take some photos of the corals now and again in a month with your current photoperiod. Shorten it and see how the growth changed after a month. Lengthen it and see how the growth changes after a month.

 

[MiddletonMark]

"Ratings" for reflectors will be even less useful, unless they provide a map of the PAR over horizontal and vertical dimensions

Here's part 1, and that's what they're doing:
http://www.advancedaquarist.com/issues/mar2003/feature.htm
[part 2 in the archives too]

Heck, they test a `painted white' canopy along with some common ones [double ended on part 2 I think]

Some great work out there to check out.

 

[JB NY]

In my opinion, "PAR ratings of MH lamps" can only be used as a very rough guide and only then for comparing one lamp to another. It is almost impossible to make inferences from the "ratings" as to how much light corals will be receiving at various locations in a tank.

Depends on how you are using the data. If you are thinking of upgrading your lamps, and already know what PAR vales you get in areas of your tank. You should be able to look at the PAR for you lamp in the data then compare it to other lamps and see what kind of a percentage increase you can expect. That with some of the pictures that have been taken of lamps over tanks can give someone a very good idea of what to expect. If used this way, a very good inference can be made.

Of course not everyone owns a quantum meter but still, on a basic level, you can use the data to see if another lamp that looks very similar has more or less PAR than you are currently getting with the lamp over the tank. Taken this way the info can be very helpful as well.

"Ratings" for reflectors will be even less useful, unless they provide a map of the PAR over horizontal and vertical dimensions. If all that is provided is the PAR at a certain distance from the centre of the reflector, it will tell you very little as some reflectors may concentrate more light towards the middle and others may provide a better spread. The former would need to be raised higher to provide an even lighting, lowering the PAR received by corals whereas the latter could be placed lower. [/B]

That is exactly what was done. Individual reading were taken from 169 points aligned to a grid, this was done at 6", 9", and 12" from the reflector. The resulting grahical plots give an excellent idea of hot spots, spread, and intesity fall off for the reflector.

Ultimately, however, there will be a lot of trial and error involved. In my opinion, the photoperiod should be at least 10 hours, but you could try less and see what impact it has on the growth of the corals. Take some photos of the corals now and again in a month with your current photoperiod. Shorten it and see how the growth changed after a month. Lengthen it and see how the growth changes after a month.[/B]

Completely agree. Although after trying more lights than the average hobbyist on my tank with lots of different acroporids. I can say that strong light (high PAR) of a decent spectrum (10K and above) does make a difference. Not as big a difference as water quality, but still enough to warrant some research. A lot has to do with what you are looking for in your tank, for me growth is not really a concern any more. Most of my corals are growing at very strong rates. I'm concerned with an aesthetically pleasing look in the tank, (I want the light color to be something that I find attractive) as well as good coloration and decent growth. Experimentation is definitely the key, but I do think we should be providing the corals with more than just their basic needs.

 

[johns]

Does anyone run MH on split photoperiod?

Does anyone run MH on split photoperiod?

Since I recently converted to HQI 250WDE (14k bulbs) I am a bit new to the whole MH world. I've had the MH over this current tank for roughly 2 months. I have been acclimating the corals to the MH light VERY slowly because I am in no hurry. I did the whole 2 hours on- 2hours off, 3 hours on-3 hours off, etc waiting a week or sometimes 2 before making changes.

I'm currently at 5 hours on - 2 hours off - 5 hours on. Of course for the 2 hours off, as well as an hour or 2 before and after the MH come on and off for the day, I run some fluorescent tubes (2 54W T5s in my case).

Things are looking reasonably good IMO. Colors especially are looking noticeable different (nicer).

The question I have been wondering about lately is if anyone has experimented with just leaving the MH photoperiod split like I am currently doing, with a couple of hours off in between.

I will probably progess toward a full uninterupted photoperiod, because I have never done this and I dont know yet whether things will continue to get better or not. Plus I still think I should be seeing better growth rates, although most everything in my tank is a frag anyway.

Anyone have anything to comment on this?