- A laser, water, and glass box,
an answer to 132% increase in PAR using the exact same light
but tested differently.
(upbeat music)
Water versus air.
Have we been wasting our time getting our arms wet
all these years for nothing?
Worse yet, are we leading you in the wrong direction?
Why is it nearly all of the industry thought leaders
and manufacturers test reef tank lighting in air,
but BRStv does it in water?
There's up to 132% increase in PAR with one over the other,
but which one is right?
The answer will change the way
that you think about reef tank lighting
and how it behaves in this glass box.
To get to the bottom of this, three experiments.
First one, visual.
We use this laser to explore how light behaves
in and out of the glass box.
You'll be surprised what happens here once we add water.
Second, actual measurable PAR results
with a water filled tank versus open air.
The third experiment, this isn't a one size fits all answer.
The difference depends on the lens,
but it all starts with this laser.
The most important takeaway today
is to understand how light reflects and refracts.
Anyone who's seen a mountain scene
reflected off of a lake has an idea
of how light can be reflected off a water surface.
Refraction on the other hand,
changes the angle or path of light
as it passes through different density mediums
like air, glass, and water.
Check out how this arrow pointing right
changes direction to left,
when we put it behind the glass of water.
The arrow hasn't changed.
What's changed is the path that the light takes
between our arrow and our eyes.
Reflection and refraction play very real roles in our tanks.
In less than a minute, it will be fairly obvious
that testing reef lights over a fixed height grid in air
has near zero value for setting up a light for a reef tank.
A grossly inferior way to compare lights against each other,
and the reason why wider angle
or diffused scattered light bouncing off the glass walls
produces higher success rates in our reef tanks.
To demonstrate this, we mounted a green laser
nine inches above our two foot cube test tank.
There are six distinct effects that you'll see.
First in an empty tank.
A small amount is reflected off the glass
to the bottom of the tank,
but the vast majority of the laser light
passes right through the glass onto the floor.
Not surprising because glass is transparent
and if it didn't let light through,
we wouldn't be able to see what's inside.
Second, after we filled the tank with water,
some new behavior is observed.
Notably most of the laser's light enters the water,
but some of that light is reflected
off the surface of the water back into the room,
not all that different than the lake scene
that we've mentioned before, but also responsible
for much of the light spill above the tank
on the wall or ceiling.
Third, when the laser's light transfers from air to water,
it changes paths or refracts.
Straight up and down,
the light takes the same straight path,
but that light that hits the water at an angle,
refracts inwards, it bends inwards
toward the center or the bottom of the tank.
This is an effect of light passing through
a less dense medium of air to a denser medium of water.
The most common way to explain this
is to imagine our light wave is a car,
traveling on pavement, which is fast,
but the wheels suddenly hit a slower medium,
like a field of grass.
Straight on, both of the car wheels would hit the grass
at the same time and the car would simply slow down,
but stay on the same straight path.
However what happens if the car's two wheels
hit the grass at an angle?
Well when the first wheel hits, that side of the car,
it'll slow down and turn inward.
When the next wheel hits the grass, it'll slow down as well,
and then continue on in that new straight trajectory.
Same thing with the laser's light wave,
which has width like two car wheels.
Straight down, the laser passes right through,
but at an angle, it takes a significant turn inward
as it transitions from the air
to a denser or slower medium of water,
essentially focusing or redirecting much of the light
down into the tank, rather than towards the edges.
Fourth, now that there's water in the tank,
very little of that light now passes through the glass,
but instead the water causes the light
to be reflected back into the tank,
essentially capturing the light
and creating new angles of incidence,
wrapping those corals in light.
Best seen in how corals,
which would otherwise be in dark areas of the tank,
are able to survive off of reflected light.
Fifth, if you look closely,
most of the laser's light is not reflecting off
the inside surface of the glass,
it's actually passing right through that glass
and reflecting off the outside edge of the glass.
You can actually see the in and out of the laser,
which is about as far apart as the glass is thick.
This effect is essentially a combination
of both refraction and reflection working together.
The light ray passing through the glass,
which has a different density than water,
changing direction, but now at an angle,
which is likely to be reflected back into the tank
rather than through.
Only the widest angles near the top of the tank,
do the lasers pass through, but what does will now take
a sharp change in direction towards the ground.
Likely responsible for that glow on the floor
around many tanks, even those with hoods.
Sixth, this is where this all comes together.
What about the back of the tank, which is painted black?
Black absorbs light, so it does just that.
All the light that passes through the glass,
rather than be reflected back into the tank,
the paint absorbs nearly all of the laser's light.
This effect is something that we see
in nearly all the BRStv Investigates on lights,
where the back couple rows are always dimmer.
So in theory, it's pretty obvious how
both the glass and water change
how our reef tanks' lights behave in an aquarium
versus a grid and air.
But the proof is in the measuring.
Will all of these effects
increase or decrease PAR in the tank,
and will it be to a degree that matters?
And the answer is yes.
To find out we did our three-level,
108 point PAR measurement in water
with the HYDRA 64, ReefLED 90, and the Neptune SKY.
All that are individually tested at ideal mounting heights.
We also tested the same with a grid and air
with the sensors the exact same distance from the light
as the water test.
Here's the net result.
With the Hydra, the 108 point average in air was 214,
but in the glass box of water, it was 296.
Mean the reflection or refraction increasing the PAR 38%.
With the ReefLED 90, which is a wider angle light,
the 108 point average and air was 103,
and the actual tank of water, 177 PAR.
Meaning reflection or refraction increasing the PAR
an impressive 71%.
With these wider angle lights,
it's almost like you're not even testing the same light.
It's so different.
The larger form factor diffused Neptune SKY,
the 108 point average in air was 224,
but in our test tank 367 or 63% higher.
To give you a scope of what that means,
224 is near the very bottom of our SPS sweet spot for PAR.
In fact, the entire bottom of the tank
is closer to the LPS range.
Whereas when we tested with water,
the 367 average is near the very top of the SPS range
with the entire bottom either above or in that range.
These varied results of 38 to 71% better
tease up our third experiment,
and one of the historical largest issues
with testing lights.
When I started reefing the industry thought leaders
all did part testing in air.
Problem was that greatly favored focused lights,
like halides with small reflectors
that focused all that light into the air grid
and punished large form factor lights like T5's
with wide angle reflectors,
which spilled a ton of light outside of the grid.
The net result of that is most reefers believed
that halides had that punch that SPS needed,
but T5 didn't or were inferior to the task.
We would later find out in an actual reef tank
or a glass box of water, 250 Watts of T5 light
was not only considerably more average PAR
than a comparable 250 watt halide,
but the larger form factor wider angle light from T5's
also distributed more light, more evenly,
even at the bottom, mean more punch as well,
all the result of factoring in reflection,
refraction and testing in the intended environment.
In our third experiment, we look at exactly that.
The punch to the 36 points at the bottom,
where we're likely to see the biggest benefit.
How much does the refraction, reflection,
and glass help the Hydra 64,
which is a narrow angle lens,
to create that punch at the bottom.
Then versus the wider angle ReefLED 90
and the larger form factor Neptune SKY,
which are going to rely on that refraction and reflection
to create the punch to the bottom.
With our Hydra, the 36 point bottom measurement
in air versus water went from 148 to 243 or 64% increase
in the bottom of the tank.
Solid performance, but not as dramatic as the next two,
because the lenses of the Hydra do a good job
of getting it down there on their own.
With the ReefLED 90, the 36 point average at the bottom
in air was an average of just 67,
but it goes all the way up to 156 in water or 132% increase.
This matters, because again,
the 67 is the bottom end of our LPS range
where the 156 is at the top.
A 132% makes it a dramatically different light source.
Same thing with the Neptune SKY,
the 36 point average in air was 132
and way out of SPS range, but in the wet aquarium,
the average rises all the way up to 324 or 113% increase.
That's the top end of our SPS range
at the bottom of the tank,
a dramatically different result in air versus water.
So much so that the air data would likely cause reefers
to both by the wrong light or even the wrong technology,
and then set them up incorrectly as well.
The biggest takeaway for me is a test tank
needs to be close to the size of its intended use
to get the best readings.
Most of today's lights are designed
for close to a two foot area
and why the 60 cube is our choice,
but with something like the AI Prime,
an 18 inch cube would be a better choice,
and why Randy added the 18 inch cube
to his recent Investigates on the Prime.
However, there is an obvious next question out there.
Now that we know how to test them,
how do we use that data
to get the right tool for the job the first time?
The answer is a playlist right here, the LED's showdown,
where we review the top 20 lights,
and for the first time, against each other.