- Anyone with a reef aquarium
knows that good water flow
is key to having healthy
corals and a beautiful tank.
Today, wanna take a look at why.
(upbeat music)
Hi, this is Wayland from Marine Depot
and thanks for tuning in.
In the early days of reef-keeping,
we had to use bulky power heads
to get the water moving in our tanks.
The flow pattern was all wrong
and we were blasting
corals like a power washer.
Today, we've got compact
cool-running flow pumps
and wave pumps that make recreating
reef-like water motion much easier.
But do you know the
science behind the benefits
of water movement in nature
and in our reef tanks?
We'll discuss the basics of water flow
and the benefits it brings
to our aquariums as well
as we look at how it can benefit
your corals specifically.
In nature, reefs are exposed
to many kinds of water movement.
The flow patterns range
from steady, mild currents
to cyclic wave action.
Waves and tides constantly flush the reef,
washing away waste products
and bringing in nutrients
and suspending plankton.
Since most of the reef's
inhabitants are sessile,
meaning they don't swim or crawl around,
food, nutrients, gases
and waste are managed
by currents and waves.
Without water movement, the reef ecosystem
would collapse into stagnation.
The same is true in our reef aquariums.
You can't rely on the
filter's output to adequately
stir up a reef tank.
To understand why, we'll have to look
at industrial water treatment.
It is a well-known principle
that suspended particles
will fall out of a solution
in a low flow environment,
especially if there are
baffles that further
slow down the flow.
That's the principle behind settling tanks
used to purify waste water.
Organic and inorganic
particles like bacteria, algae
and mineral particles
are heavier than water.
Gravity causes the solids to
fall to the bottom of a tank
when water movement is low.
The same thing happens in a reef aquarium.
Rock work, corners of the aquarium,
and the filter sump create low flow zones,
allowing suspended debris to
settle and collect as sludge.
You'll also see fine debris settle on
and behind live rock and even corals.
Low flow prevents debris
from making its way
to the filter sock and other
mechanical filter media.
Like it or not, a reef aquarium
is an ideal settling tank
with plenty of low-flow
areas that collect particles
of debris.
Here's the fluid dynamics formula.
But you don't need to do the math
to know that sludge
happens in an aquarium.
Reversing your reef's tendency to act
as a sludge collector is easy.
No matter what size tank you've got,
there's a flow pump made for it.
Increasing water movement
will keep the debris suspended
so the filter can remove it.
But water flow is more than
just keeping your tank clean.
So far, we've only looked at
the physical aspects of water movement.
Most of the marine life in
an aquarium are microscopic.
You can't see them, but there
are billions of microbes
at work to keep the ecosystem functioning.
While some of these
microbes are in the water,
most are living on the surface
in crevices of the live rock,
sand, and even form
specialized communities
under coral colonies.
These micro environments
range from oxygen-rich
aerobic zones on rock
surfaces to anaerobic
denitrifying niches inside rock forms.
These colonies of microbes
do most of the work
of purifying and recycling waste products
and also the nutrients in the aquarium.
But the fact is, they
depend on water currents
to bring them the substances
they need to do their job.
Think of reef rock and sand
as a big biological filter.
It needs water circulation
to keep it functioning efficiently.
Circulation pumps bring
the water to the rock
and flush away waste
materials and sediments
that could interfere with the microbes
living on and in the rock.
Solid surfaces like reef rock,
even though they're submerged,
have a special thin layer of water
right at the rock-water interface.
This is called the boundary layer.
It's a thin layer of water
that essentially does not move.
Fish, macro algae, and even
corals are all surrounded
by a boundary layer.
Oxygen, CO2, waste, and other nutrients
have to pass through the boundary layer.
The lower the flow, the
thicker the boundary layer.
Wave makers and flow pumps
force water across the rock,
reducing the boundary
layer and making it easier
for the microbes to do their
job purifying the water.
In the earliest days of reef keeping,
marine biologists recognized
that captive corals
did much better when there
were wave-like currents
in the holding tanks.
We've known for a long
time that corals in nature
are surrounded by a one to
two millimeter diffusive
boundary layer, or DBL.
Water motion keeps the layer thin,
allowing easier transfer
of nutrients and waste.
To mimic wave action, Doctor
Walter Adey and others
experimented with surge
tanks and dump buckets,
pioneering the way for today's modern
wave-making flow pumps.
Zooxanthellae algae
inside the coral tissue
work with the coral pods to
share energy-rich substances
and recycle nutrients.
Corals rely on water
currents to bring food
and essential elements for many
biologically necessary processes.
These processes include
photosynthesis by zooxanthellae,
carbonous skeleton building,
reproduction, and nutrient
and dissolved gas exchange.
There are a number of studies
that show coral metabolism
as measured through
photosynthesis and calcium carbon
production is directly
affected by water flow.
The research is conclusive
that slow water flow
inhibits coral growth.
But there's more than
just a DBL at work here.
An international team of researches
discovered that corals
just don't passively wait
for water currents to
overcome the boundary layer.
The research revealed
that reef-building corals
are covered with microscopic cilia
that constantly beat,
creating mini vortices
that spin in the opposite
direction of water flow.
Corals actively disrupt
the boundary layer,
increasing transfer of
nutrients to the coral,
and waste products out, by up to 400%.
That test was run in a tank containing
acropora, montipora,
seriatopora, protopalythoa,
palythoa, and an opalytha discosoma.
These findings show how
important water flow is
to the metabolic processes of corals.
Corals need water flow to
maximize growth and health.
Coral cilia can influence a boundary layer
but only up to about two
millimeters from their surfaces.
Increasing water flow
is essential to bring
the boundary layer down
to one to two millimeters
so corals can manage
the nutrients and gases
that affect growth.
Increased flow also maximizes
a micro community's ability
to remove nitrate ammonia and other waste.
And finally, a flow pump will keep debris
from collecting behind a live rock.
Wave makers and flow pumps
do more than make coral sway
like they do on a reef.
Water flow is an integral
part of the coral biology
and necessary for keeping
corals in captivity.
We no longer need to
build our own surge device
to have great flow for our corals.
Today, we have an array of
purpose-built water pumps,
many with tide and wave
mimicking functions
built right in.
No matter what size of reef you have,
there's a flow pump for you.
We hope you found this
information helpful.
If you did, let us know by
clicking the like button below
and feel free to share
it with your friends.
Until next time, take care
and happy reef keeping.
(upbeat music)
