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aquarium utilizes a closed loop circulation system. The
intake is through the strainer located on the bottom of the
photo and the return is through the bulkhead on the right hand
side. In order to protect the pump, it is important to
keep any intake strainers clear of algae and other debris. |
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Today
aquarist utilizes a myriad of devises and techniques to create these
very important currents in the reef aquarium.
In order for you to create an effective system it is
important to understand the difference between filtration and
circulation.
Filtration
is the deliberate removal of particulates and dissolved materials
from your aquarium water. For a more detailed description see the February 2003 issue of Advanced Aquarist.
Circulation is simply moving the water around the aquarium.
The reason that I make this important distinction is to draw
attention to a common misunderstanding regarding the source of the
aquarium’s water movement.
As with
any complex subject in this hobby, people are always looking for
(and giving) rules of thumb. With
regard to water movement in reef aquariums, many authors will
advocate at least 10 times the volume of the aquarium per hour.
So if you have a 100-gallon reef, you should be moving around
1000 gallons/hour. This
is a fine starting point as long as you understand that this does
not mean that you need to move 1000 gallons of water in and out of
your aquarium.
Many
reef aquarists use some sort of overflow in the tank to take water
to an external container called a sump. In the sump various tools
such as protein skimmers, carbon containers, reactors, etc. filter
the water. The water is
then returned to the aquarium.
This is referred to as an open loop.
The volume of water that flows through this loop need only be
3-4 times the volume of the tank (not 10+).
This is the filtration flow rate. The rule of thumb that was
mentioned earlier refers to the circulation rate in the aquarium.
This number takes into account, not only the return from the
filter, but circulation from various other pumps as well.
I cannot tell you how many times people have come to me and
asked how they can quiet there filter down on their 90 gallon tank
because they are trying to put 900 gallons/hr through their
overflow.
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It is important to
remember that any sort of turnover formula that you use should only be a
guideline. Match your circulation scheme to the types of animals that
you will be keeping. For
instance, many books will give information about where the corals are
found in nature so that you can house them accordingly.
The rating systems may vary from book to book, but you can get a
general idea for a starting point.
Once your tank is up and running, it will be important to
experiment with the placement of your corals until you find an area
where they prosper.
Let’s look at a
hypothetical set up, and go over some important plumbing tips.
For example if you
are setting up a standard 75-gallon reef tank you will need to give some
thought as to the filtration/circulation components that you would want
to include. Most reef
aquarists find it helpful to install an overflow, which skims the
surface water and takes it down to the sump. The flow of water into this sump is going to be equal to the
amount of water that is added back into the aquarium.
The next logical
question is “How many gallons per hour do I need to run through my
sump?” This number is going to be dependent upon whatever you are
using your sump for. A
typical “Berlin system” that just uses a protein skimmer will only
need the volume of water that the skimmer can handle.
So if you have a skimmer that has 200-300 gallons per hour coming
out of it, then running several times this amount past it is
unnecessary.
If you are using
your sump as a refusium, that houses a live sand bed or macro-algae,
then theoretically you would only need to run enough water through it to
maintain the same chemistry as the display aquarium.
In other words, as long as you don’t see any differences
between the chemistry of your sump to that of your aquarium then you are
putting enough water through that filtration part of your system.
Keep in mind that
most of your filtration is taking place in the aquarium, so that is
where you should spend your dollars creating the water flow.
Through the use of power heads or a closed loop system you will
be able to quietly and efficiently create a great deal of water
movement. As a general
rule, it is better to produce this current from multiple outlets rather
than one strong return.
Now let’s
consider some various ways to move water around in the aquarium.
The first method
that I would like to mention is the use of air pumps and blowers.
The use of airlifts is a very cost effective way to move large
volumes of water. These are
two very important considerations for everyone.
Unfortunately this type of system is not practical for most
hobbyists’ displays. It
would take a large number of airlifts to create the volume of water flow
that we would like to have for our reef aquariums.
And this volume of air bubbles creates a lot of salt spray that
would create a very real maintenance issue.
In my opinion however, airlifts are practical for commercial
applications.
Most aquarists use
multiple water pumps to create the necessary water movement in their
aquariums. There are
numerous companies producing just about any size pump that you would
need. For most reef keepers
this means a pump that can withstand saltwater, is quiet and inexpensive
to run. Keep in mind that
these pumps will be running 24/7 and on a larger system, the energy
costs add up. So if you are
designing a larger system, it will definitely pay to do some research.
To learn more about pump terminology and design check out sights
such as www.pumpworld.com
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The majority of
reef aquarists will use either external pumps (outside the aquarium) or
internal pumps, know as powerheads.
These pumps come in all sizes and flow rates.
Power heads: There
are a few brands, such as Tunze, that produce air cooled pumps that
mount above the aquarium. Although
these are very powerful and do not heat the water as much as submersed
types, they are quite expensive. When attempting to ascertain how many
pumps you will need and how large they should be it is prudent to first
look at the types of corals that you would like to keep, and from what
area of the reef they are commonly found.
Scientists have
used flow meters to find out what sorts of flow rates are common on
various areas of natural reefs. These
flow rates are given in inches per second which is a measurement of
velocity. These velocities
do not mean much to the general hobbyist since most of the pumps that we
use are rated in gallons per hour.
Dana
Riddle published an interesting article on water motion in the reef
aquarium and arrived at some guidelines that I have found match my
experiences. He suggests
that aquariums with soft and large-polyped stoney corals should use (1)
powerhead equivalent to that of a Maxi-jet 500 (rated at 1.75ft. /sec)
per 24” of tank length. For
aquariums that contain SPS corals use (1) powerhead equivalent to a
Maxi-jet 1200 (rated at 2.45 ft./sec) per 12” of tank length. There
are a number of submersible pumps on the market today and, like so many
other aquarium products, I recommend consulting fellow hobbyists and
your local fish store for advice.
Regardless
of the type of pump that you choose there are a few things to remember.
Always have some sort of protection securely mounted on the
intake of the pump. A
prefilter screen or sponge will prevent animals and debris from being
sucked up to (or in to) your pump! Just be sure to make this prefilter
easy to access for regular cleaning.
It is important
that the pumps you select are water cooled (not oil).
This way you never have to concern yourself with a potential
contaminate. Also, since
these pumps are water cooled, they will produce some heat. At this time
I prefer the Maxi-jet line by Aquarium Systems for tanks less than 40
gallons.
They are small, powerful, and relatively inexpensive.
If you are keeping
a larger aquarium (over 40 gallons) then you may want to consider using
a closed loop system. Basically this is when water is taken out of the aquarium and
fed directly into an external pump and then returned to the tank. The return to
the aquarium can be through a hole that is drilled into the side of the
aquarium or simply over the back with a plastic pipe. Technically, a
canister filter is a closed loop, but for these discussions I will be
referring to circulation pumps only. Some advantages to this method are:
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You can move a
great deal of water without a lot of noise
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There is less
heat gain to the aquarium
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This system is
less unsightly since you don’t have pumps in the aquarium
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You don’t
have to worry about the suction cups that hold the powerheads to the
glass wearing out and potentially damaging a coral head with a rough
jet of water.
If you decide to
use this type of system there are a few things to keep in mind:
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Be sure to
plan out the overall layout of the reef so that you can place the
intakes and returns appropriately
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You can run
this type of system by simply running the intake and return over the
back of the aquarium instead of drilling holes in the tank.
This method is not as clean looking, but it allows you to set
up this type of circulation on an existing tank.
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If you do
decide to drill the aquarium, do not drill these holes on the bottom
of the tank, because if a pipe or pump housing were to crack you
would loose ALL of your water (and hence your livestock). The closer you are to the surface, the safer you will
be.
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Be sure to
include shut off valves and unions so pump maintenance or
replacement can be done with a minimum of hassle.
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Remember you
can use your overflow boxes to hide the returns
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Be sure that
the pump that you are using is below the water level so that the
front of the pump (refered to as the volute) will always have a
supply of water.
In
an attempt to create a more natural type of water flow (i.e. Less
laminar and more surge-like) aquarists have developed a variety of
methods and devices to randomize the currents produced by aquarium
pumps. One of these is the use of a “wave maker”.
This device gives power to the circulation pumps at random
intervals thereby creating more random water patterns.
This reduces the number of areas without good water movement (AKA
dead spots). Although these
devices do give the corals a break from one unidirectional flow, they
don’t really turn on and off fast enough to really produce a surge
action.
There
are a few potential drawbacks to these devices.
Some pumps do not fair well with being turned on and off
continually and will fail prematurely.
Also, some powerheads have a noisy rattle during start-up and the
use of a wave maker may drive you out of your living room.
Be sure to seek out specific product testimonials from fellow
aquarists or your local aquarium shop before putting one of these
systems together.
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In an
attempt to create even more natural water movement in the aquarium,
some aquarists utilize (aptly named) surge devices.
These systems employ a container (usually a plastic trash
can) that is positioned above the aquarium. Water from the aquarium
is pumped into the container from a pump located in the aquarium or
connected reservoir. When the container is almost full, a large PVC
pipe in the container rapidly siphons the water back into the
aquarium creating a rapid surge of water.
This rapid flushing is a very effective way to reproduce the
type of surge action found on reef flats.
Although corals seem to do very well with this type of water
movement, it does have some drawbacks.
Because
the whole apparatus is above the aquarium it can be unsightly to say
the least. Noise can
also be a factor. The
continual sound of flushing of water into the aquarium may be more
than some can deal with. Then
there is the matter of bubbles that create salt spray that gets on
everything. This type
of system would work well with an aquarium set into a wall, with an
access room behind it. There
have been a lot of modifications to these devices that make them
more users friendly. To
find out more about this type of set up you can check out www.ozreef.org
for detailed plans.
Another creative solution
to the issue of randomized water movement is the use of some sort of
mechanized return system. One
of my current favorites is the Sea-Swirl.
This device attaches to the back of the aquarium and
oscillates the return from your main return pump or closed loop pump
back and forth once every minute. Although these units are somewhat expensive, they do solve
many of the problems that wave makers have.
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| .This
new powerhead by Tunze uses a propeller to create a current
that has a broader stream than other impeller driven pumps.
This design allows these pumps to move a large volume of water
without the potentially damaging affects of a narrow
discharge. These units also have an accessory controller
that allows you to vary the speed of the motor, thereby providing
a more surge-like environment. |
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Proud
sponsor of this column
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Basic
Tips for Water Movement:
Here
are some basic tips to consider when plumbing your reef
aquarium. I realize
that this list could go on for days, and everyone has different
opinions, but I am compelled to pass on a few tricks that might
keep money in your pocket and water off your floor.
They are in no particular order of importance:
- Although
it may seem like a lot of trouble at first, always take the
time to properly size you pumps and piping.
Although aquatic systems may operate with the
improperly sized equipment, it is important to remember that
all of this comes down to getting what you want and need for
your animals and saving money.
There is enough expense in this hobby without paying
for oversized pumps and inefficient filters.
- Try
to avoid designing a system that needs constant attention.
It’s always a good idea to make your sump large
enough to go several days without a top off.
- When
installing filtration pumps, always use shut off valves and
unions so that you can make pump service and replacement
easy.
- Be
sure to cover any clear piping or reactors that are exposed
to light with some sort of shading material to prevent algal
growth, especially coralline algae.
- Try
to design a system that does not depend on any sort of check
valves to prevent flooding.
The high levels of organic and inorganic material
that will eventually accumulate in your reef will tend to
make these devices jam up. So avoid drilling the aquarium in any way that will make
you dependant on a device that may fail.
If you do choose to install a check valve for any
reason, be sure to purchase one with a clear housing so that
you can see whether it’s operating correctly. Also, just
as with pumps, use unions and shut off valves so that you
can service them easily.
- Never
undersize the pipe or fittings that are on the suction side
of a pump. This
is known as “starving” the pump.
As a general rule, use whatever size fittings and
lines match the intake with that particular pump.
If there is a question consult the manufacturer.
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Avoid
making any pumps or prefilters hard to get to. This is especially important when trying to hide
circulation powerheads in the reef itself.
These pumps will need service, and whatever you stack
over the pump will have to be removed in order to get to
them. This can be especially heart breaking if corals, sponges
etc. have grown in these areas, and have to be destroyed.
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Always
use some sort of ground fault interrupt. Salt water with
electricity…enough said.
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When
plumbing the aquarium, avoid adding unnecessary bends and
turns when ever possible.
This adds unnecessary head pressure to the system and
will cost more to run.
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Always
have a redundant source of circulation.
Many people will try to circulate the water in their
tank with only one pump.
This may work fine if you have a large pump with
several returns. Just remember that any pump can fail, and you never want
to design a system that will leave your tank without any
circulation if just one pump fails.
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If
at all possible, place drain and return lines either in an
overflow box, or high up on the tank, so that in the event
of a broken or leaking line, fitting or pump your tank
won’t drain completely.
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If
you have to use hose clamps underwater, always use all
plastic ones. The
metal hose clamps (even stainless steel clamps) will rust.
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It
is important to periodically shut off the power to your tank
to simulate a power outage.
This will allow you to make sure that any back flow
precautions that you have taken are still effective.
This is important for many people that use small
holes in their return lines to prevent back siphoning.
These holes often become clogged and need to be
checked on a regular basis.
I
have to admit that working out the means of filtration and
circulation for reef tanks has to be one of my favorite aspects
of building a reef system.
I’m sure that many of you will find that developing a
system that works for you will be both enlightening and
gratifying. I hope
that by reading this article that you will take away some bits
of knowledge that will help you to develop a circulation system
that will make your reef aquarium a success.
To
access our Reefkeeping Basics forum to discuss this article, click here
Copyright 2003 Advanced Aquarist's Online Magazine
