Rethinking standard approaches to lighting and current - Meet the WTD ratio

[DBrinson]

Foreword:

I've read many articles and publications and for the ideas I have picked up over the years I can't possibly begin to give credit where it is due. At one time I would have kept my mouth shut, because the world of hobbyists was overrun by self-appointed experts and exploitative sales interests who passed bad advice around until it became accepted by hobbyists. It was futile to try and debunk much of this nonsense.

When wetwebmedia was compiled, I read every one of those articles as they were posted, it was like an addiction, to see the elite team of minds Bob Fenner assembled to make sense of the perverse world of reefkeeping thought.

More recently (in this RS community) I have been impressed by how "good" ideas that work have taken hold in the larger community, so that even in the chaos of an open forum, the best ideas float to the top.

That I would write out my thoughts on current and lighting is a reflection of how much respect my fellow reefers have earned, and how much I have learned from your own well-informed, well-explained advice while reading all of your posts.

That being said, I can say that most approaches to lighting and current I disagree with on a very fundamental level.

I know aquarists tend to look at flow in terms of GPH and lighting in terms of Watts/gallon.




The main trap we fall into is, that for convenience's sake we tend to cram

• our watts into "spread out" light sources
• our current into "point" sources

But in the world's reefs, the opposite approach is used to illuminate corals and create flow ... and for good reasons.

I spent a tremendous amout of time snorkeling in the Keys, from a 22 foot sailboat when I was a tyke. There were times I spent one hour underwater and received four hours worth of sunburn. However, when the water was "flat" the effect was not so pronounced.

The sun is a "point" source of light.

Ocean currents are a "spread out" source of current, most of which is ultimately driven by forces on the water's surface.

The brilliant lighting that is supplied to the reef originates from a point source (Mr. Sun) and is magnified by waves much like a magnifying glass focuses the sun's rays on a hapless ant. If you could watch the shimmering light on the reef in slow motion you would see very bright random lines of light, sweeping over the reef. There is no separating lighting and surface current any more than there is a separation between a photo of a blood cell and a lens in the microscope used to view it.

Right now corals are listed as "moderate lighting", "high lighting", "low lighting", "versatile". But this does not address a coral's needs ... coral xooanthellae feed on shimmers of focused light from the sun ... not from a steady wattage.

Consider a coral that lives in 30' depth in a part of the reef where the waves "crest-to-trough" height is 1' on a typical sunny day.

Such a coral's wave-to-depth (WTD) ratio is 1:30 ... this is very important to determining the amplification of light the coral should receive due to surface currents. A tank that is 30" deep should aim for 1" ripples at the surface in order to supply the coral with its favorite "light food". If 1/2" ripples are the standard in the tank, the same coral could be placed 15" under the surface with the correct color temperature light applied. I have long suspected this is why some have success with SPS corals in shallow water under intense lighting only, while others have made them work in deeper water with less intense "point source" lighting. (i.e. Metal Halides)

The surface currents capable of producing this rippling effect would then inherently give the coral the underwater current it needs .... if due respect is also given to the terrain the coral lives in that shelters it from the current and light.

Why surface current? That's how it is done in the ocean. The best measure of randomized, intense current in a tank should be found at the surface. Not in GPH, but in the ripples that are visible as opposing currents collide, both focusing the light onto the corals and forcing water downward in surges.

The focus on surface ripples should not be limited to current and lighting. Aquarium manufacturers can design tanks to allow for wave action and surface ripples that are unpredictable as they peak and trough. The goal should be irregularity every bit as much as peak-to-trough capacity. That smooth golden suntan you get snorkeling won't happen if the waves all pass in the same direction.

Thus a coral's complete lighting and current needs could be specified by its:

• WTD ratio
• Optimal color temperature (or natural ocean depth range)
• Terrain

Nothing else is needed, if the hobby and suppliers of equipment measured performance by the randomized surface-driven currents they create, and by the magnification of point sources on corals at different depths, I believe the hobby would advance along many fronts in ways it seems unable to now.

Needless to say, I do not buy into the PAR approach to lighting. It is based on very good research and it corrects a lot of overlooked issues in lighting analysis. But I think it misses the ultimate point, the nature of sunlight on the reef calls for what we in engineering call "dynamic" rather than "static" analysis. Coral polyps are little prisms of light; they need ripples of light from different angles, not just intensity in their general location.

Disclaimer: I am not trying to throw away the benchmarks that have been useful to aquarists over the years, but to offer an alternative point of view that I feel would be more useful and informative, while pushing the hobby forward into more productive advances.

Please comment, critique, and shower me with your enlightenment, fellow RS minds!

 

[redneckgearhead]

Ok, so do you believe we should try to mimic waves, and how do you find out how deep in the water your coral came from? Most are listed by the amount of light they require. I find what your saying very interesting and sounds very plausible, but not sure how we can better mimic the ocean (I know were not even close in these tiny boxes). I do have surface agitation as I believe alot of reefers do because of the o2 exchange and other benefits that it brings, but Im not sure how we can have any more waves in our tanks. And like most I have t5ho lights that do not seem to cause the "shimmer" as do LED's and MH lights so should we switch to these types of lights to create this? I hope I have understood your thoughts and conveyed mine as well. I love posts that make me think!

 

[DaveK]

DBrinson's post does make some interesting points. The methods used today, while better that the watts per gallon, still do not account for everything. I am not sure if the proposed WTD method is any improvement. It's an interesting idea, but I don't see how it can easily be evaluated. We'd have to measure the lighting in the ocean and record the surface water conditions too. This would also need to be done over a period of time. Then we'd need to scale the process down to see if it still applied in a reef tank that is only a few hundred gallons at best. I'm not sure the process would scale down.

The other thing I see is that people have great reef tanks using a lot of different lighting types, and most corals do just fine under T5 or other good fluorescent lighting, with doesn't produce any shimmer. We'd have to see if it made a major difference in the corals, if a point source of light was used and we got the shimmer.

I think the problem comes down to how do we test these ideas to see if they are correct, and to see if they aid our reef keeping.

When it comes to reef systems there is comparatively little scientific research. Most of what we know is form someone trying an idea and seeing if it works better than the existing methods. If it does, people adapt the new method. For example, at one time trickle filters were considered the ideal reef filtration system. It was a major improvement over under gravel filters, but nowadays trickle filters, while still used by some, are generally considered less than ideal compared to a berlin type sump with a refugium. We got there by people trying a new method and it worked better, but I don't know of anyone that actually did a serious scientific study to find out why one method was better than the other.

 

[steved13]

Nice food for thought, thanks for taking the time.

I have always questioned the watts per gallon, I realize that on many levels "it works", but I've always known watts don't really make a difference unless comparing apples to apples. if watts were the only factor, You could hang a 1500 watt hair dryer above your tank and light it very brightly, but we all know that won't work. How much of the energy (the watts) is producing light vs producing something else (mostly heat).

Your theory on the shimmering, or focusing of the light is interesting, the real question is; is the focusing neccessary, or even beneficial? You could say since when you go swimmming in the ocean, on a sunny day you get more focused rays, so maybe that's the way nature intended it, and it's better, however we know, those focused rays are really not healthy for us...how do we know the corals aren't better off without them? Many have great coral growth under T5s with no shimmering. I do have to admit, I like the looks of the shimmering and it does look more natural.

 

[DBrinson]

Great questions/points Scott, Dave, Steve! Woke up this morning to 1-2-3 thought provoking posts.

Ok, so do you believe we should try to mimic waves

We should use oscillating or alternating currents along the surface of the tank as current sources and use the height of the resulting "ripples" as a measure of effectiveness. In order for the tank to qualify the surface ripple pattern would have to be random enough so that three photo stills of the waters' surface will always yield three separate "peaks" of the turbulence.

and how do you find out how deep in the water your coral came from? Most are listed by the amount of light they require.

Exactly! Merchants in particular are fixed in their ways when it comes to realizing the importance of these factors.

Let me use some publicly available maps of the acropora region in the FL Keys as an example of what we should see.

The data above are just an example using the weather report, but if one considers the range of the acroporas (small lower right inset above), and compares the range against a compilation of the the wave height values (leftmost map) divided by the depth values (upper right map) one would have a rough range for the WTD (wave-to-depth) ratio that acros thrive under.

I find what your saying very interesting and sounds very plausible, but not sure how we can better mimic the ocean (I know were not even close in these tiny boxes). I do have surface agitation as I believe alot of reefers do because of the o2 exchange and other benefits that it brings, but Im not sure how we can have any more waves in our tanks.

Outstanding question, I strayed from addressing this in the OP so as not to sound commercial. I personally use Sea Swirls to generate random swift surface currents, in fact over the past week I have been tweaking my Sea Swirl outlets to generate the greatest ripple effect I can. (as shown in the photo in the first post)

Granted, I've spent way, way too much time playing with Sea Swirls, watching the ripple currents and observing the light and current effects on the corals and inverts underneath. I can attest that the surge currents in the depths of the tank are directly related to the surface ripples, and that the elimination of dead zones in the tank is best when the currents on the surface remain horizontal, the downward currents all a by-product of current collision on the surface.

There are other ways to generate similar currents with other products, but I'll leave it to the other posters in the thread to expound on that. The difference between one Sea Swirl and two was phenomenal ... yet the corners of the tank's surface remained predictable in wave patterns. With three I have been able to eliminate even that.

And like most I have t5ho lights that do not seem to cause the "shimmer" as do LED's and MH lights so should we switch to these types of lights to create this? I hope I have understood your thoughts and conveyed mine as well. I love posts that make me think!

I'm not advocating anyone giving up a system that works for them, though I would encourage you to rip out your powerheads and focus on current sources that oscillate on the surface of the water. I always encourage other reefers to go with MH lighting as well, though we all know it isn't necessary for success.

I use actinic t5's myself, you can get good results with corals using t5ho's!

My main point in writing this was to encourage an industrywide change in how we rate and supply corals with their lighting and current flow needs.

DBrinson's post does make some interesting points. The methods used today, while better that the watts per gallon, still do not account for everything. I am not sure if the proposed WTD method is any improvement. It's an interesting idea, but I don't see how it can easily be evaluated. We'd have to measure the lighting in the ocean and record the surface water conditions too. This would also need to be done over a period of time.

Well, all of this data is already out there, and in use by the collectors of coral in the industry. Walt Smith and friends once had an excellent writeup on the waters around Fiji years ago, the wave patterns around the reef are as connected to the coral locations as the depth of the water.

Then we'd need to scale the process down to see if it still applied in a reef tank that is only a few hundred gallons at best. I'm not sure the process would scale down.

I achieved outstanding coral growth and hardiness in a 90 gallon with a pair of Sea Swirls and a pair of 175W MH's. My SPS corals grew both upwards and downwards, until they fused with the rock.

The other thing I see is that people have great reef tanks using a lot of different lighting types, and most corals do just fine under T5 or other good fluorescent lighting, with doesn't produce any shimmer. We'd have to see if it made a major difference in the corals, if a point source of light was used and we got the shimmer.
I think the problem comes down to how do we test these ideas to see if they are correct, and to see if they aid our reef keeping.

The recent analysis of lighting that led to the PAR values was based on observations that MH's of equal wattage far outperformed VHO's, CF's, and other tubular lighting.

I am suggesting that the discrepancy had less to do with photosynthetic light that reached the corals, and more to do with the way in which the light was applied.

The parallels in industry are legion. If you are slicing through steel with an industrial laser, a "pulsing" laser beam will outperform a "steady" laser beam of equal wattage every time.

And you can find SPS corals thriving in relatively "dark" water in the Keys, in places where wave action overhead is high, and the rippling effect of sunlight is well-pronounced. I'm convinced it's the extremely high energy in the "bright" shimmering lines that makes it possible.

When it comes to reef systems there is comparatively little scientific research. Most of what we know is form someone trying an idea and seeing if it works better than the existing methods. If it does, people adapt the new method. For example, at one time trickle filters were considered the ideal reef filtration system. It was a major improvement over under gravel filters, but nowadays trickle filters, while still used by some, are generally considered less than ideal compared to a berlin type sump with a refugium. We got there by people trying a new method and it worked better, but I don't know of anyone that actually did a serious scientific study to find out why one method was better than the other.

I remember my first "trickle" filter, in 1985. The owner of the LFS in Wilton Manors, FL termed it a "reef system" and built it himself out of filter padding and acrylic. Now they call them "wet/drys" apparently.

Nice food for thought, thanks for taking the time.
I have always questioned the watts per gallon, I realize that on many levels "it works", but I've always known watts don't really make a difference unless comparing apples to apples. if watts were the only factor, You could hang a 1500 watt hair dryer above your tank and light it very brightly, but we all know that won't work. How much of the energy (the watts) is producing light vs producing something else (mostly heat).

Not only that, if you dropped it into your tank you'd probably end up on Channel 6 News. (Noone try this at home!)

Your theory on the shimmering, or focusing of the light is interesting, the real question is; is the focusing neccessary, or even beneficial? You could say since when you go swimming in the ocean, on a sunny day you get more focused rays, so maybe that's the way nature intended it, and it's better, however we know, those focused rays are really not healthy for us...how do we know the corals aren't better off without them? Many have great coral growth under T5s with no shimmering. I do have to admit, I like the looks of the shimmering and it does look more natural.

Well, nature intended humans to live in caves, before the housing industry and constructed homes ripped us from our natural habitat. (You know, we should feel like victims, fish who are transported to tanks are often called victims, even though they often live fat and happy lives safe from predators) There's only one other creature on Earth who gets sunburn, and I ate him for breakfast this morning next to my scrambled eggs.

But your question is outstanding. I have a few ideas on how to measure this, for one, I have often wondered why the xooanthellae found inside of coral polyps is not cultured and exposed to different types of lighting to measure its health under different lighting schemes. Photosynthesis is directly measurable, I measure it in my seagrass tank every night with an ORP probe.

I believe the proof is "in the pudding", quite literally, and would love to see lab tests on xooanthellae species as well as corals under various lighting applications, with surface current and refraction of the light taken into account.

 

[steved13]

I knew the swim in the ocean, wasn't the best analogy and would get a "not our natural habitat" response, but I knew you'd get the point . You might want to check, many animals can and do get sunburn.

I'm not a laser expert, but I think the pulse laser is used so that it doesn't generate as much heat into the target so you get a cleaner cut, not sure that's any help to your theory.

 

[Reefmack]

Interesting thread!

 

[TylerHaworth]

This is my brain on Metal Halides......

 

[Triggerjay]

Also, something to note regarding shimmer from T-5's, and similar lighting. It may still be there, but not visible to the human eye. There are many different wavelengths of light that are not visible to our eyes. This shimmer could very well be there under this light as well. Another factor to throw in is the frequency of the shimmer. Halides could have a much slower frequency rate than say a t-5, which may be very rapid. Possibly faster than our little eyes can see. In the US, our power comes in at 60hz a second. At 60 cycles a second, I could see and understand why if the simmer occurs with t-5's there is a possibility that we would not be able to see it. You also have to take into account the ballast, which could change the frequency rate even farther.

Jason

 

[DBrinson]

I'm not a laser expert, but I think the pulse laser is used so that it doesn't generate as much heat into the target so you get a cleaner cut, not sure that's any help to your theory.

An excellent point! (fits my theory quite well though)

Less heat ... because each pulse is applying extremely high energy for millionths of a second, followed by a lapse before the next burst.

I spent quite a bit of time in a laser lab during my graduate research, though my makeshift office was in the microwave lab next door. That lab is closed/renamed now, but here's a link I googled that describes it at the time I was there.

The idea of a pulsed laser is that instead of generating a continuous beam, a continuous source of power is used to charge up an internal beam and release it in bursts, so even a weak power source is able to generate ultrahigh energy for short durations. This is very much like the effect of rippling waves as they refract the sun's light. Less solar power is necessary to zap the xooanthellae with the burst of energy they need to photosynthesize. The lower heat absorbed by the coral polyps may well be another advantage of the phenomenon.

You don't have to be an engineer or a certified laser technician to understand the benefits of surface current refracting sunlight to separate it into "bursts" and "lapses" as it penetrates the water above the reef.

Photosynthesis is roughly a two stage process, only the very first stage involves the absorption of light, and that stage is much shorter than the second stage, where the light energy is converted to sugar. By supercharging light in a bright flash, then giving the photosynthetic cells time to process the energy before the next band of refracted light passes over the cell, the waves above the reef may be doing just what you say, without heating coral polyps more than is necessary.