- If your LEDs look like this
which are perfectly spaced evenly across your tank,
you might wanna stick around.
Because although it looks appealing to your eyes,
today, we find out
if that aesthetically appealing light placement
also benefits your corals, or can we do better?
(upbeat music)
Today we're digging up over 20 past
BRStv Investigates videos on light testing,
pulling out hidden information for ideal light spacing,
and then sharing our best data driven
answer to the question.
What is the ideal way to space 2, 3 or 4
light fixtures over my reef tank?
Spoiler alert, evenly balanced spacing is not the answer,
but let's find out what is.
There's over 20 different light configurations
of varying brands, shapes, and sizes to look at today,
and they're divided into four groups.
The two fixture group, the three fixture group,
the four fixture group,
and in a group of its own, eight AI prime fixtures.
What we're looking for,
is at what light light spacing interval
does the average part in the left and right tank edges,
come within 75% or more of the average part
in the dead center.
Meaning that we've eliminated any hotspot in the center
where the lights intersect,
and spread that light out towards the edges
for ultra flat par distribution.
With that, let's first look at the two fixture groups data
made up of 11 different lighting options.
For two fixtures over a 48 inch tank,
dividing the tank length evenly into thirds,
shows us a balanced placement.
Has each fixture perfectly centered
at 16 inches from the left edge,
and 16 inches from the right.
However, looking at the data, only two of the 11,
actually meet or exceed our 75% power distribution goal
without adjusting them.
The Atlantik Orphek V4s, and the Philip CoralCares.
And when you see the large form factor of these two lights
it's really easy to see why,
a pair of Orphek at 24 inches each covers exactly 48 inches,
while the Phillips are 18 inches each,
and also able blanket the entire 48 inch tank
from edge-to-edge, out of the box.
The remaining nine pairs of lights,
just come up short when placed
at the same 16 inches on center,
with the Orphek Compacts
having the least amount of even spread,
as we can see by the outer edges only measuring 45%
of the center average part.
While the Radion XR15s come the closest to our goal
but still short at 57%.
The most interesting part is what happens
to all nine pairs of LED combos,
when we start to spread the two fixtures apart.
Every single lighting option each mounted
at their own respective optimal mounting height,
surpasses the 75% goal.
When we center each fixture at 13 inches
from the left edge and 13 inches from the right,
upwards of 88% even coverage across that entire tank.
It's pretty hard to argue
that simply mounting a pair of lights
perfectly balanced over a rectangular tank,
is going to yield the optimal results,
especially when nine completely different lights
each with their own unique lenses,
LED arrays and module sizes,
all show the best spread performance
when spaced wider than what is aesthetically appealing.
But let's see if the same holds true
for the group of three, and four light fixtures.
In the second group,
five different light brands start evenly spaced
over our 48 inch tank, at equal increments of 12 inches.
And the results for uniform spread
are pretty far away from the goal.
Again, it's the Orphek Compacts that wind up
with the least at 54%, while the Gen5 Radion XR30
show slightly better performance
with the left and right edges at 62%,
of the center warm spot.
In order to find the optimal spacing for three fixtures
we leave the center module fixed in the center of the tank,
and then move the left and rightmost modules outward.
When we do that, what we find is the AI Primes
require the widest spacing to achieve to 75%,
with the left Prime centered at 8 inches from the left edge,
and the right Prime centered 8 inches from the right edge.
The Orphek Compact were similar
but they found better spread,
with the outer lights just at 9 inches centered.
The remaining three all hit 75%
with a spacing of 10, 24 and 10 inches on center.
Again, just by spacing these lights wider
than evenly balanced, wound up creating upwards of 24%
more even distribution of light throughout the entire tank.
The third group of four light modules are next
where an evenly balanced light spacing,
would have each module centered
at 9.6 inch increments across the tank.
But the closest we come to our 75% goal with this spacing,
is 72% from the four Kessil A360Xs.
With that we slid the extreme left and right modules outward
as well as the center two further apart,
this time spreading the light more evenly
from 83% upwards of 88%.
As you can see,
there are a couple of configurations that accomplish this
the two AI Hydra options spaced at 7, 17.2, 17.2 and 7,
and the Radion XR15 and A360X,
at 8, 17.2, 17.2 and 8.
So should you just slap lights
above your tank evenly and call it a day,
or do you need a Palm meter to get this right?
I'd say, a good rule of thumb here,
you don't need a Palm meter
to achieve better spread performance.
If you have two lights to mount
just put them a bit wider than what your gut would tell you
by about two to three inches each,
three lights, definitely keep one centered,
and move the outer two slightly closer to the edges.
Again, about 2-3 inches,
four lights, this one is pretty close to optimal already
at a balanced spacing.
However, for those looking for a slight edge performance
you should consider moving each module
slightly away from center to reduce that inevitable hotspot.
But there's still one more group that we didn't mention yet,
and that is the grid of 8 AI Primes
over that same 48 inch tank,
instead of toying with hundreds or even thousands
of various space and configurations.
To find that optimal spread,
we mounted each one to basically cover
a one foot by one foot square area,
and then used zoning to balance out the distribution.
By keeping the outer 4 primes at 100% intensity
and then reducing the center four Primes to 40% intensity,
we were able to eliminate the hotspot in the middle
and achieve an 84% even spread across the 48 inches.
This is something very unique
to using a large grade of individual modules,
where we cannot only control the distribution,
but we can also use zoning to increase the par
in strategic areas.
But of all the data that we recovered today
there's still the lingering question of,
how many lights do we need in the first place?
2 or 3 for LPS, 3 or 4 for SPS.
Is there a good starting point,
a rule of thumb or a guide to help?
The answer is yes,
and you can find that answer in Ryan's FAQ video right here.
So check it out.