This design is being released in Reefkeeping
Magazine as a service to the readers of Reefkeeping.
By releasing this idea/design here for the public to see,
it now becomes public domain. This means YOU can make one
or have someone make one for you. In the interest of sharing
information, if you see room for improvements or additions
for more functionality, please post them for public use.
As is the case with most things in life,
the reefkeeping hobby is always seeking ways to advance and
improve. One area in particular where improvements have been
sought is in providing food sources more appropriate for reef
tank inhabitants, namely, live foods. This interest in providing
live foods has brought its own set of challenges (or opportunities,
depending on one's viewpoint). The first challenge to be met
was to develop techniques to culture live food and insure
the quality (and quantity) was significant to warrant the
effort. In the last couple of years we have seen articles,
websites, and discussion boards devoted to educating the reef
keeper on the basic, and sometimes advanced, methods of culturing
live foods. The term 'live foods' has grown to include brine
shrimp, rotifers, ciliates, copepods, and numerous microalgae
with each having specific benefits for the food chain we try
So let's pretend that we know all we need
to know about culturing live foods. Wow, we got real smart,
real quick! But this brings us to the next challenge in reef
keeping, to wit, "How do we get the food into the tank?"
Sure, we can dump some food in the tank every evening. This
works, and works within acceptable terms. But is there a better
way? Is there a way to incorporate 24 hours/day, seven days/week
drip-feeding? Is there a method that doesn't require the aquarist
to carry three bottles of different cultures to the tank everyday?
The answer is maybe, just maybe.
If we look at how reefs in nature feed,
we might find an answer. Natural reefs are fed by the tides
surging food onto the reefs. With every surge, food is swept
over the reef. Already, some reef keepers are applying surge
type movements for current. What if we could use this same
idea to feed the tank? What if we could provide an almost
constant supply of food to the tank in surges or small 'prescribed'
doses? It would really be a benefit if we didn't have to stand
there and manually apply each feeding to the tank.
Well, I thought it was a good enough idea
to spend some time thinking about how this might be achieved.
After spending a little time considering the possibilities,
I developed an idea that has worked quite well. This idea
required the use of acrylic. Not being gifted in working with
acrylic, I enlisted the expertise of George Weber of www.geosreef.com
to give me a hand with the construction. I showed him the
drawings for this new idea. We discussed it back and forth
and the outcome, looking somewhat like the result of a cross
between a skimmer and calcium reactor, was the "Geosapper"
While looking a little complex at first
glance, the "Geosapper" has proven to be well worth
the effort. A major benefit to the "Geosapper" is
that it contains no moving parts. The only maintenance after
initial setup is a periodic cleaning, which is easily accomplished
as each section comes apart by loosening a few screws.
The "Geosapper" can operate without
moving parts because of the integration of small surge devices.
So, in order to understand the operation of the "Geosapper",
we need to understand surge devices. Surge devices work on
a siphon. Water fills the container, and when the water level
reaches a point higher than the highest point of the surge
tube, the water is siphoned out. The siphon continues until
enough water has been removed that a siphon break occurs.
This stops the siphon (surge) and allows the container to
refill before surging again.
With a basic understanding of surge devices,
the best way to describe the operation of the "Geosapper,"
is to break it down into its three distinct sections:
Top Section - Phytoplankton, Middle Section
- Rotifers, Copepods, Ciliates, etc..., Bottom Section
- Brine Shrimp. (The brine shrimp are in their own, and last,
section because they tend to eat any and everything they encounter).
The top section is nothing more than a
holding station for phytoplankton. Fill the top section with
phytoplankton, easy enough. The choice of species or type
of phytoplankton is purely up to the user. Each section is
equipped with an air bubbler to maintain a high quality of
live food. There is an option to use two different types of
phytoplankton, but we'll discuss that in the section below.
From this area the phytoplankton then drips into the middle
section via a drip valve.
The drip valve is the key to proper operation
of the "Geosapper." The drip valve regulates the
flow rate into the middle section. The importance of this
valve will become more clear as I proceed. The picture to
the left shows the drip line with the inline drip valve connected
to the top section. The installation of the drip tube makes
adjusting the flow rate very easy. With the end of the drip
tube above the water line of the middle section, each drop
can be observed. This is critical to ensure the proper flow
The middle section houses a batch of rotifers,
copepods, ciliates, etc. For the purpose of this article we
assume we are only using rotifers. As the phytoplankton is
dripped into the middle section from the top section, the
rotifers are fed and allowed to multiply. Once the level in
the middle section reaches the surge point (a level just above
the surge tube), a predetermined amount of phytoplankton and
rotifers are surged into the bottom section. The surge leaves
behind enough phytoplankton and rotifers to allow the continued
reproduction of the rotifers. In most cases this is enough
to sustain a continuous culture for a long time period. This
is ultimately determined by the size of the actual "Geosapper"
and the size and frequency of the surges.
The surge tube can be seen in the middle
of the picture titled "Middle Section". Also, towards
the bottom of the middle section, the air bubbler can be seen.
Again, the air bubbler ensures oxygen distribution in the
water and provides a low, steady current to keep the contents
of each section in suspension. The middle section has an addition
of a fill/vent tube. This is PVC tubing which runs from the
middle section to the point just even with the top section.
The fill/vent tube is used to restock the rotifers (should
it be necessary) without having to take down the entire unit.
The fill/vent tube also allows air to enter and leave the
section for proper surge performance.
The bottom section is used to house freshly
hatched brine shrimp. The brine shrimp will load up on the
phytoplankton and rotifers being surged in from the middle
section. This surge from the middle section raises the level
of the bottom section, thereby causing another surge action
to occur. This last surge takes phytoplankton, rotifers, and
brine shrimp into the tank.
The picture on the left shows the air bubbler,
fill/vent tube, surge tube, and the output to tank.
The unit in operation. Green food coloring was added
to the water just for purposes of the test.
The adjustment of the drip valve flow rate
controls the frequency of the surges. A faster drip rate equates
to a more frequent surge or more food into the tank.
The surge amounts are determined by the
size of the surge tube. The shorter the surge tube, the less
the amount that will be surged.
Using Two Types of Phytoplankton
The top section has an extra connector
in the middle of its base. This can be used to connect to
another drip line for a different type of phytoplankton without
having to mix them in the top section. This will allow two
distinct types of phytoplankton to be fed to the middle section
and then surged through the "Geosapper."
Sizing the "Geosapper"
For the unit pictured here, the total volume
is approximately one gallon. The Top Section holds approx.
½ gallon of phytoplankton and each of the other sections
holds approximately one quart. The acrylic tubing used for
each section can be larger in diameter and length to accommodate
To determine the appropriate size for your
application, we need to know how to calculate the amount of
the surge. For example: Using a 8" acrylic tube with
a 0.5" surge tube, we can calculate the volume using
the formula (pi)(r^2)h, "r" is the radius of the
tube and "h" is the length of the surge tube. So,
our example is 3.14*16*0.5 = 25.12. Then we take that number
and divide it by 12^3 (12^3 = 1 cubic foot). We now know we
have 0.014 cubic feet of surge. Since 1 cubic foot equals
7.5 gallons, we see 0.014 * 7.5 = 0.10 gals or 12.8 ounces.
Knowing each surge is 12.8 ounces and the
top section of the "Geosapper" holds 64 ounces,
we can calculate the number of surges per fill of the top
section. This is done by dividing 64 by 12.8. This gives us
5 surges per fill.
To change the amount of each surge, we
simply change the diameter of the acrylic tube or the size
of the surge tube. We can also change the size of the top
section to adjust the maximum number of surges per fill.
The top section could be filled with salt
water, the middle section left empty (with Surge Tube removed),
and the bottom section filled with brine shrimp or other suitable
live food. Using the "Geosapper," one could surge
feed live food to seahorses to provide constant live food.
Because we are adding saltwater to the
tank, care must be taken that the salinity of the tank does
not change drastically. The easiest way to accomplish this
is to remove the same amount of tank water as the amount of
phytoplankton added to the top section of the Geosapper.