Lighting affects both the beauty of the reef tank as well as the health of the organisms within it.
single reflector for each individual bulb.
These tend to sort of wrap around the top
half of the bulb and have several folds in
the polished aluminum, designed to send
more light down into a tank. Therefore, we
tested both. Note that if you’re thinking
about buying the components to put a
retrofit lighting system in a pre-existing
canopy, this will be especially important,
as you can choose which type of reflector
Let’s get on to how we tested some T- 5
bulbs with a single sheet-type reflector
that has a single fold down each edge,
and what we found. To start, we got
a prefabricated fixture that holds four
T- 5 bulbs and includes a single polished
aluminum sheet mounted above the bulbs,
and we covered the entire reflector with
black electrical tape. We put the bulbs in,
set the fixture up over our testing rack,
and fired it up. One little thing to note
here is that we waited about half an hour
to start taking readings, since it takes a
while for systems to warm up and the light
output to stabilize. Output changes a good
bit depending on bulb temperature.
After everything was ready, we took a
series of readings to measure PAR using
our meter. Readings were taken at fifteen
positions under the fixture: five from end
to end, and three across (see the grid on
the figures). Note that the bottom of the
fixture was approximately 5¼ inches from
the top of the light meter’s sensor.
After finishing that up, we pulled out the
black tape, got the fixture warmed up again,
and took the same series of readings. This
let us make a direct comparison between
the light that would be going down into a
tank with and without the reflector.
With the reflector blacked out, the
highest PAR reading we got was 191 µMol/
m²/sec. We also found that the average
PAR was 155 µMol/m²/sec, which was
calculated by adding all the readings
together and dividing the sum by 15.
With the tape pulled off the reflector, the
highest PAR reading was 435 µMol/m²/sec,
and the average PAR was 342 µMol/m²/sec.
That’s quite a difference to say the least,
as the average PAR went from 155 to 342
µMol/m²/sec, 220 percent of the original!
Thus, it should be quite clear that the
use of a sheet-type reflector can make a
heck of a difference in the amount of light
going from a T- 5 bulb to the critters in
We next tested a different fixture with
three T- 5 bulbs, but this one included
individual reflectors for each bulb. They’re
the type that has numerous folds, along
with a little ridge that runs right down
the middle of the reflector. This little ridge
is supposed to angle away the light going