Water Movement In the Reef Aquarium
Roy Seine - July, 1997
Water movement in the Reef aquarium is very important to the lively hood of those creatures that
we keep. Without adequate water movement, our corals would die on their own excretions.
Therefore, we as aquarists must provide that life giving current to our slimy little friends.
First I would like to talk about surface movement and what it accomplishes. The movement of
water across the aquarium is to create ripples along the surface that agitate the surface water, so a
protein slime doesn't occur. Another benefit is that it helps in the aid of carbon-dioxide exchange
at the surface of the water.
This can be accomplished by three different ways, return circulation, powerheads, and dump
The return circulation is the easiest. The pump return nozzel needs to be pointed up toward the
surface of the water and have the current move towards the middle of the aquarium. (if the return
is in a back corner)
This will create a nice ripple effect out towards the middle of the tank, away from the overflow.
Powerheads can also be used. I currently use Otto, Rio, and Maxijet pumps. The small Rio 600
is a great pump to suction cup up in a corner. Use a piece of plastic stuck in the back so the pump
will get a somewhat good direction of flow to the surface. The Otto pumps have an adjustable
nozzel that can be pointed in any direction, which is really nice. This allows you to create
surface agitation toward the middle of the tank to collide with the main return pump. This
collision creates a lot of turbulence and any SPS corals that live in that area really love it.
Dump buckets are the best for creating a fast surging motion of water across the reef. These are
very difficult machines to keep in operation and on a small tank are not worth the trouble. They
work well on large aquariums (over 300gallons) and prove to have very positive effects on the
wildlife, but they just aren't practical to those of use who have smaller tanks, or when the same
affects can be accomplished without all the hassle.
I would like to bring up the Carlson surge device. I was lucky enough to talk to Dr. Bruce
Carlson on his surge device at the Waikiki Aquarium. What they have done is taken a 50 gallon
plastic drum and a 30 gallon plastic drum and created an unique surge system. When the 50
gallon bucket is full the pump starts to fill the 30 gallon drum, when that reaches its set level the
drum is dumped into a shute and then is funneled through a 4" diameter pipe and into the
aquarium, creating a very nice surge through the reef. (Note this is on a large scale aquarium)
On to wavemakers. The commercial wavemakers are nice to have if you have the spare clams
laying around to purchase one. :) IMO the only real benefit that can be had from commercial
wavemakers is the easy start of powerheads and the ability for them to create slower currents at
night. Here is what most hobbyists have done...
Most of you are probably familiar with electrical timers. The use of an electrical timer and a
powerhead together work very well to create random surges of current throughout the reef. The
timers are also much less expensive and can be found at almost any electrical hardware store.
The best ones are the type you can set little plastic pegs into the timer circuit, thus creating on
and off cycles when you want them.
Now, just a short talk on currents and corals. For most corals the more current the merrier
applies. In personal observations, even leather corals need a fair amount of current. I have found
out if they do not receive good current, especially around the base, they will begin to rot. This is
caused by the inablity of the coral to get rid of waste that has accumulated upon its skin and not
having enough current to blow it away.
Even when a soft coral is placed in front of a 250 GPH pump, not all the debris will come off.
This should kind of give you an idea how much current these corals do require, and we as
aquarists are just not providing enough current. I must point out that strong currents directed at
softcorals all day long is not a good idea, but a random, 5-10 min burst will keep them happy.
There are exceptions to every rule of course. Fox coral (Nemezophyllia Turbida) does quite well
in very low currents and will close up if strong currents are directed toward it. Also, the giant
clams that many of us keep are also low water current creatures. The Euphyllia family is usually
kept in mild currents also, but I have found they enjoy a heavy water surge once or twice a day.
SPS (Small Polyp Stony Corals) require a vast amount of ever changing currents. This requires
many powerheads and or a very powerful surge device. The need for high water velocity is to rid
the coral of it's own wastes, this is true with any coral. Most SPS's will do quite well in a very
turbellent enviroment where the water is moving past them in a strong burst like movement.
Dana Riddle pointed out that large heads of acropora will significantly reduce the water flow
about half way through a colony. This fact means that large volumes of water must be moved
through the aquarium to satisfy SPS's current needs. IMO that means we aren't even coming
close to the water movements in nature and i don't expect us too either.
Now for a short description of how water currents are achieved in my 60 gallon reef tank. This
tank is equipped with seven powerheads inside the tank, all rating from 150 GPH upto 650 GPH.
Powerhead placement is as such: One 150 GPH powerhead in each upper corner. Everyother one
is pointed to the center and up to create a surface ripple. All the powerheads are operated on light
timers, which were purchased from the local hardware store.
The other two are pointed up to create a surface ripple that runs along the tank's front and back
walls in opposite directions. The other three are placed in among the rockwork to create random
flows within the rocks and lower corals. This provides the current for the low level deniziens
such as Slipper coral and open brains.
All timers are set for random starts and stops. All powerheads come on at once at 1pm in the
day to create a surge effect throughout the reef and stir up any loose sediment. This cycle lasts
for 40 minutes. The total flow output during this time is a little bit over 1300 GPH. Then
powerheads are set from 1 minute running time to several hours, switching on and off randomly
throughout the day.
I have found that this combination of powerheads creates a very pleasing water flow to the
corals and to me, since i enjoy watching the tenacles sway in the currents. One important note,
before i open it up to dicussion...
You should have a surface powerhead pointed toward your overflow from the opposite end of the
tank, this creates good water movement into your sump. I hope you have all enjoyed my
opinions on water movemement in the reef aquarium. For those of you who would like to view
my tank please visit:
Last modified 2005-02-07 05:55