My FishRoom friend Rod
Andrews told me about a single-pass (non-recirculating) calcium
reactor that he made from one of those water filter cannisters
that you can get at Home Depot and similar places. The
simplicity of Rod's design appealed to me. I had one of
those filters lying around, so I decided to build one, even
though I already had a perfectly adequate single-pass reactor
that had been serving me well for a year or so. Building this
water filter-based reactor takes less time than reading this
document.
At this point you may be wondering why
a single-pass reactor is a good idea.
The particular water filter I started from is an Instapure K-50,
from Teledyne Water Pik. I bought it at a local home center
about three years ago. You can use whatever you can find
locally, though these "plans" may not apply perfectly if you use
a slightly different water filter.
Anatomy of the filter
These water filters consist of a clear plastic cylinder with a
threaded lid at the top. The lid contains two connections: one
for water input and one for water output. My filter has 3/4"
female pipe threads for the connections. I prefer to premix the
aquarium water and the CO2 using a bubble counter
designed for that purpose, so my calcium reactors need only two
holes in them: a single input and a single output. I discuss my
bubble counter at the end of this article.
Look at the underside of the filter's lid. You can see that
the water input port just empties out into the top of the
reactor. The output port is different. There is a tube in the
center of the lid, oriented vertically when the filter is in
the normal upright position. The output port on the lid is
connected to the inside of this tube. The tube is only a few
inches long, basically extending down to the bottom of the
lid, but not into the filter's body. We shall attach a PVC pipe
to this tube, so that the output of the reactor will come from
the bottom of the reactor. This ensures that no CO2 gas will
leave the reactor.
The filter also has a small plastic ring that sits at the
bottom of the filter, and serves as the base for whatever
filter module you would normally use in the filter. This ring
is a removable piece. We shall use this plastic ring to
support the base of the tube that carries output water from
the bottom of the reactor up through the output port of the
lid.
Making the connection to the lid tube
We need a fairly
water tight connection between the tube we add and the little
stub tube on the inside of the lid. Fortunately, that stub tube
is tapered, so we can get a nice seal just by sliding an
appropriate fitting on. I found that a 3/4" PVC coupling
works. The insides of PVC fittings contain a shoulder, which the
PVC tube seats against. The shoulder in
a PVC coupling is midway through the coupling, and is basically a
small section of reduced diameter. It is this shoulder that seals
against the filter tube, not the main inside diameter of the
coupling. Since the diameter at the shoulder is not part of the "PVC
spec," different manufacturers are free to use different dimensions
there. I found that one coupling worked, whereas a coupling from a
different manufacturer was too loose. You will just have to experiment
with different fittings and pipe, and find something that works for
you and your filter. If you have access to a lathe, you can easily
bore out a pipe or fitting to the required dimension, but if you can
find off the shelf parts that fit, then you can build the whole
reactor using only a hand saw to cut PVC pipe.
Making the connection to the base ring
The plastic base ring inside the filter has three flexible
prongs on it. These prongs fit inside the filter module that you
would normally use in the filter. The prongs also fit nicely in
a 3/4" PVC coupling. Now, we have a 3/4" coupling at the bottom
of the filter, and one at the top.
Pipe
We must cut a length of PVC pipe to cover the span
between the lower and upper couplings. It can be somewhat tricky
to get the length right. You have to push the upper PVC fitting
into the stub tube on the lid to a certain depth in order to
get a seal. If you do not get a seal, then nothing forces the
water to pass through the aragonite bed, and the reactor may be
ineffective. So the PVC pipe cannot be too short. But if the pipe
is too long, you will not be able to close the reactor (screw on
the lid) tightly, and it will leak.
What to glue
I glued the length of PVC pipe to the upper coupling, but
nothing else. In particular, the connection between the top PVC
coupling and the stub tube that is part of the lid must
remain a slip fit, so that you can attach the lid with the tube
already in the reactor, imbedded in sand, and so that you can
remove the lid without pulling the tube out of the sand.
Connections to the filter
As I said earlier, my filter
has 3/4" female pipe threads for the input and output. Many
people prefer to use standard "airline tubing" for their reactor
lines. Airline tubing is 3/16" ID. I prefer to use 1/4" ID
tubing, which you can get at local home centers, and
elsewhere. I purchased some 3/4" male thread to 1/4" hose barb
connectors from MSC. The
item number 48712525 at MSC gets you a 10-pack for about
$2.50. MSC has a $25 minumum order.
Filling the reactor with sand
With the reactor open and the loose parts before you, fit the
lower coupling onto the prongs of the filter's plastic lower
ring. Plug the PVC pipe into the other side of the lower
coupling. I am assuming that the other end of the PVC pipe has
the upper coupling glued onto it. Now place the PVC pipe into
the filter body, with the filter's lower ring at the bottom.
The PVC tube may be somewhat
wobbly at this stage, because nothing supports it except at the
bottom, and the lower plastic ring in the filter can move around
a bit.
While holding the PVC tube roughly centered in the filter
body, dump your aragonite sand into the reactor. Fill it right
up. Now screw the lid on. The lid's stub tube should fit into
the top coupling of your PVC tube, and form a seal.
Filling the reactor with water
You now have the problem
that the reactor is filled with sand and air rather than sand
and water. Because the reactor's output comes from the bottom of
the reactor, the gas in the reactor will be trapped. How are you
going to get that air out? Turn on the water flow to a high rate
(a solid flow rather than the drip that you will use in normal
operation), turn the reactor upside down, and the air will exit
the reactor. After all the air is out, turn the reactor right
side up.
A bubble counter
CO2 enters through the top connection. The
white object is a check valve. The gas is released into the
bubble counter at the bottom of the rigid airline tubing that
appears in the center of the main tube.
Water from the aquarium is pumped into the bottom connection
by a small powerhead located in the sump of the reef setup, or
by a tee off of the main system pump or the skimmer pump.
Some of the CO2 dissolves in the water within the bubble
counter, and some exits the bubble counter still in gas form. A combined
CO2 and water product leaves the bubble counter through the side
wall of the tube.
From there, it goes through the plastic needle valve, which is
used to control the rate at which the aquarium water passes
through the calcium reactor. Premixing the CO2 and aquarium
water lowers the pH of the mixture to about 5.8, and ensures
that calcium carbonate is highly soluble in the fluid that
passes through the valve. This high solubility in the valve
prevents the valve from clogging with calcium deposits.
After water comes out of the righthand side of the needle
valve, it will be taken via flexible tubing to the input of
the calcium reactor.
At this point your reactor is finished and operational. I do
not intend this document to teach you how to use a calcium
reactor. From here on out all of the standard reactor usage
lore applies.
Add or View Comments
Last modified: Thu Feb 03 19:51:35 Eastern Standard Time 2000