Q: Are calcium reactors complicated?
A: No, calcium reactors are in fact very low-tech devices; they
just look complicated because of all the attending equipment.
Essentially, a calcium reactor is a sealed vessel; filled with
calcium based media and an external circulation pump which
constantly cycles water in the reactor through the media. The
reactor is also connected to a metered source of C02. This CO2 is
bubbled in at a slow rate to mix with the circulating water and via
chemical reactions, dissolves the media into calcium carbonate.
Q: How do I hook up my calcium reactor?
A: Well, there are a couple of components, and pieces/parts
which you will need in advance to get your reactor working.
Typically, the reactor is fed with water from the tank, either from
special plumbing, a T-connector in your return line, or a siphon.
You will want to have this worked out before you start. You can
then fill the reactor with media, and then complete the plumbing.
Make sure you leave plenty of slack in the various lines for
maintenance. Of course, you will also need a source of CO2, and
bottled sources work best for this purpose. The connection between
your CO2 tank and reactor should be plumbed with CO2-proof tubing.
You should apply Teflon plumbing tape to all large threaded
fittings, including your bubble-counter to help prevent leaks. Once
these are in order, you need only drip the effluent at a slow rate
into your tank.
Q: Is CO2 gas dangerous?
A: The official designation of CO2 is Non-Flammable.
While CO2 is not classified as dangerous like chlorine gas would
be, CO2 can most certainly be toxic. If one were to breathe only
CO2 you would quickly asphyxiate. CO2 is certainly worthy of
respect, and is a compelling reason to be diligent about avoiding
leaks in the CO2 portion of your reactor.
Q: Do I have to use bottled CO2, or could I just as easily use a
yeast-reactor or similar mechanism for adding the CO2 to the
A: While it is certainly not a requirement, it is perhaps the
most consistent means of applying CO2 to your reactor. After the
initial cost of the bottle, the refills are on average about $10 or
less for a 10-pound tank. Yeast reactors require constant
maintenance, and can't really keep up with the demands of a
Q: Is this the only way to supplement calcium in my tank?
A: No, there are many options of which the reactor is only one:
two-part solutions, kalkwasser, and natural processes are all
viable mechanisms for calcium additions to your tank. The most
compelling reason to use a calcium reactor is to stay ahead of
demand from the tank inhabitants, and as a side benefit, to
automate the supplementation.
Q: If my calcium is already low, will a calcium reactor
A: The quick answer is yes and no, and in fact you can make your
problems worse if you're not careful. Like any supplementation,
one needs to move slowly as this equipment is brought to bear on
your system. The effluent - the stuff that comes out of the reactor
- can have a very low pH and this can in turn shift the pH of your
tank towards the more acidic end of things. A well-tuned calcium
reactor can easily bring low calcium levels up to a more useful
level, but it's best to have things in the right range before
you start adding effluent from the reactor.
Q: Fair enough, is there a recommended flow rate of CO2 into the
reactor, and a recommended flow rate out of the reactor?
A: Again, this will vary from system to system, and there is a
direct relation between the CO2 inputs, and the effluent outputs.
The best way to explain would be to imagine we are talking about a
Cool Aid reactor, we have a container of rocks that turn into
Cool-Aid, and the CO2 dissolves the rocks. If you constantly add
CO2, but barely let out any of the juice, the juice will become
very concentrated. The opposite is also true, if you let water flow
out of the reactor at a high rate, but don't add much CO2, the
resulting effluent will be very weak and watery. Somewhere in the
middle there is balance.
Q: That was a terrible example, what else you got?
A: Sorry, say this time we've got a container full of
crushed coral… and the CO2 will slowly dissolve the crushed
coral. The same applies, except in this case we are more concerned
with the pH and dkH of the effluent rather than if it is tasty,
Cool Aid. These two factors are now crucial because they will
affect the calcium uptake of your reef-inhabitants in addition to
other chemical processes going on in your tank. So, the take home
message here is this: you must test quite frequently when you first
set up the reactor to arrive at a drip and bubble rate which works
best for your tank.
Q: What is the target(s) I am shooting for?
A: Again, this is subjective - on average, a dkH of 8 - 12 is
considered good. A calcium level of 350 - 400 is likewise adequate.
Your pH will vary over the course of a day, but should be in the
range of 8.0 - 8.4. The effluent should be have a pH range of 6.5
to 6.8 - the dkH should hopefully be at the least 20, or even off
Q: So are you telling me I just bought an alkalinity
A: In essence, yes - the calcium reactor excels at replenishing
the alkalinity/buffers in your system. It just so happens that the
replacement solution is high in calcium, so it's a win-win as
Q: Hey I still have more questions, may I ask another?
Q: Please, I've still got a lot of questions.
A: Oh, ok I suppose so…
Q: Sweet. What kind of maintenance do I need to do?
A: Ahh, good question. The media will have to be replaced on a
regular basis. How often will depend on how heavily the media is
being consumed. Probably best to check every three months at the
start, and as time goes on you will find a better period in which
to renew the media. In the interim, the best thing you can do is
give the whole reactor a good shake, once a month. This is a good
reason to make sure you have a good amount of slack on the various
lines connecting the reactor. When you swap in new media, you might
also check the circulation pump, and clean if necessary.
Q: OK, last question… can this new calcium reactor keep my
calcium at 450+ and a dkH of 12+?
A: It could, but would that be wise? More often than not,
keeping both of these numbers simultaneously high is difficult if
not impossible. In most cases, dkH and high calcium PPM are
mutually exclusive. A given quantity of water can only keep so much
calcium in solution [dissolved] before it is saturated [can not
dissolve any more calcium] and the excess will form a precipitate -
the snow phenomena that you have probably heard about. Real world
numbers are somewhere in the middle of the "ideal range"
and not at the high end of the scale.
Q: Sorry, next to last question: What should I be using for
A: There are a number of brands and also the option of making
your own. You should avail yourself to other calcium reactor users
to see what their preferences are. If you choose to make your own,
you can crush dead coral skeletons with a hammer [don't forget
the safety glasses] and put this directly in the reactor.
Q: This is really a lot more than 10 questions, I've got
another: what's the solenoid on the CO2 regulator for?
A: Mainly to avoid excess CO2 from escaping the system during a
power failure. The solenoid can also be hooked to your light timer,
so that CO2 is delivered only during the lights-on hours. You can
also connect the solenoid to a pH controller which will turn the
valve on and off based on a preset pH. A pH controller is not a
requirement, but most certainly useful.
Q: Wait, you just said something about running only during the
lights-on hours. What's that all about?
A: Well, this is depends mostly on what's going on with your
tank. Some people have problems with depressed pH [more than usual]
at night. By turning off the CO2 at dark time, you will increase
the pH of the reactor's effluent, and reduced its impact on the
Q: Oh man, I didn't buy a pH controller… do I
"have" to have one?
A: No, you don't, but you should certainly have a pH test
kit handy, and probably stock up on reagents while you are at it.
Speaking of tests, if you don't already you should also have a
dkH [hardness] test kit and calcium test kit within reach. You
shouldn't hook up your reactor without them.
Q: Does CO2 affect photosynthesis?
A: Absolutely, yes. Without CO2, there is no photosynthesis - it
is a major input in the process.
Q: Is excess dissolved CO2 a problem?
A: It most certainly can be… and often seen as the source
of a depressed pH, or say lower than normal. In many modern reef
tanks, where there are skimmers, sumps with spill-over weirs,
strong circulation and the like, the water is well aerated and so
excess carbon isn't usually a problem. Likewise, if you've
got a good crop of photosynthetic corals or macro algae, these are
going to be quite thankful for the extra CO2.
Q: How can I tell if I have excess CO2 in my tank water?
A: Easy, take a sample of your tank water and measure the pH.
Then, put an air pump to work on aerating that same sample, and let
it go for 6 to 12 hours. At the end of your test measure the pH
again. If the pH has gotten higher [by two or more tenths of a
point] then you probably have excess CO2 in your water. If not, you
need to look for other causes.
Q: Can I also dose kalkwasser while I am using a calcium
A: Sure you can, but you will probably have to reduce the amount
you have been dosing up to now. Always start by measuring your
calcium and make sure you need to do this at all - with any luck,
you can put your kalkwasser away. If your calcium is lower than
desired, kalkwasser is a great source and can help push a low pH in
the opposite direction [if that's what you want]. The
possibility to create havoc with kalkwasser additions is really
quite real. Regardless, you should always test before and after to
make sure you're not doing something drastic. Similar to other
additives, you can really put yourself in trouble if you add
wholesale without testing first.
Q: So what is my baseline? Where should I start?
A: I would start with the manufacturer's directions. Most
that I've read come with a recommendation for a bubble rate
from the CO2 and a drip rate for the effluent. I would personally
divide these in half and start from there. For the first week, you
should test your tank and the effluent several times a day. Once
you become more familiar with the equipment, and the affects of the
various adjustments that can be made, you can test a little less. I
still keep on a regular test schedule to make sure everything is
within normal tolerances.
Q: What if something goes wrong?
A: Well, that depends - I suppose the quick answer would be,
don't panic, even though that may seem like the most
appropriate thing to do. Anything you might need to do would need
to be affected over a longer period of time, so quick reactions may
make problems worse. If you take your time setting up, and
performing tests you can avoid problems before they start, yes?
Q: Just thought of another question: what's the second
A: Ah hah… you've been shopping around. Most commonly
the second chamber is either for additional media to be exposed to
CO2, and thereby increasing the amount of effluent, say for a very
large system. Or, this is chamber is only filled with media but not
provided a CO2 source, becoming a passive reactor. In this design,
the effluent from the reactor is then run through this second
chamber to let the low-pH/high dkH go to work on the raw media
within, and as a result gaining a rise in pH of the resultant
effluent coming out of the second reactor.
Q: Sweet, can you come over to my house and set up my calcium
A: Book the flight, board my dog, feed my fish, and let my
employer know I won't be in tomorrow and you've got a