Calcium Reactor Set Up
There have recently been a number of threads regarding the set up of a calcium reactor, and I thought that there might be a need for a reference. I am by no means an expert on these things, having only started using one a few months ago, but I did a lot of research before I started using one and want to pass the information along.
Calcium Reactors, otherwise known as CaCO3/CO2 reactors, are essentially simple devices. Water is fed into a cylinder filled with media, usually aragonite, along with a controlled amount of carbon dioxide. The carbon dioxide lowers the PH of the water in the cylinder which causes the aragonite to dissolve releasing equal parts of calcium and alkalinity. This calcium and alkalinity rich water is then feed back into your tank replacing the calcium and alkalinity in your aquarium. The size of your calcium reactor will be dependent on the amount of clacium and alkalinity your tank requires, i.e. a 100 gallon tank of softies has a much different calcium and alkalnity need than a 100 gallon tank of SPS.
The calcium reactor has a number of essential parts. Obviously there is the cylinder where the media is placed (hereinafter the "reactor"). In order to get water to the reactor, a feed pump is used and a Maxijet seems to be a common choice. The amount of water flowing through the reactor and back into the tank is actually quite small, and on my reactor measures about 60 milliliters a minute. In order to control the amount of water leaving the reactor (the "effluent") you will need either a small ball or needle valve that will allow you to precisely control the flow of effluent. You want to but this on the output side of the rector as it will make it easier to get a constant flow. Most reactors have a second circulation pump that circulates the water in the reactor allowing the C02 to dissolve and the water to stay in contact with the media.
(This is my GEO 618. You will notice that my reactor has a built in bubble counter , as well as a port for a PH probe which I have connected to my Aquacontroler to shut off the CO2 through the solenoid if the PH drops to low-see below. The effluent tube is not labeled, but it is the black tube running in front of the bubble counter, it has a small ball valve for effluent control on it)
Obviously you need a source of CO2 and this is where the CO2 tank comes into play. The most common sizes are 5lb and 10lb tanks although they can come much larger. The C02 tank is highly pressurized (around 1000lbs per square inch) so you need a regulator to control the amount of CO2 that is released, usually dropping the pressure down to +/- 5lbs per square inch. Next you will need a needle valve in order to precisely control the amount of C02 that is being delivered into the reactor. You will measure the amount of C02 being released into the reactor by observing a bubble counter, which can be attached to the regulator or the reactor itself. The bubble counter is nothing more than a tube filled with water where the C02 is released.
Although not strictly necessary most people use a solenoid, which is essentially a device that allows you to attach a PH controller to the regulator allowing the controller to shut the supply of CO2 off when the PH in the cylinder drops to low. If the PH drops to low, your media will turn to mush greatly hindering its effectiveness. Some reactors have a place for PH probe so that your controller can measure the PH of the water in the reactor. If your reactor does not have this, you can measure the PH of the effluent (water leaving the reactor) and I believe at least one of the vendors on this site makes a collection cup for this purpose. Please note that the effluent will have a PH of around 6.8, so your standard PH test kit will not be able to measure it (the ones I have only go down to 7)
( this is 10lb CO2 tank, with a JBJ regulator, not the best but it works. It has a built in solenoid and a needle valve controled by the knob on the right. The black tube goes to the bubble counter on the reactor itself)
SET UP
First test your tank for calcium, alkalinity and magnesium and bring them to your desired levels before you hook up your calcium reactor. The reactor is a good way to maintain levels but not a good way to adjust levels. You will also need to know what your levels were when you started so that you can adjust the reactor until you find the sweet spot where it is adding as much calcium and alkalinity as is being used.
Now that you have done all your tests and adjusted your parameters using your supplements of choice, and then tested again - it is time to get the reactor running. So you got your calcium reactor all set up as per the manufactures directions and you go to turn it on and you realize that there are a number of variables that need to be set. You have to decide on how many bubbles per minute of CO2 you will use, what the rate of the effluent (the water leaving the reactor) will be and what pressure to set the regulator to. After doing a great deal of research I decided on the following initial set up.
The Regulator
PSI should be set to less than 10, ideally between 3-4
The Needle Valve, Bubble Counter
Set the bubble counter to 30 bubbles per minute (BPM).
Effluent Rate
Adjust your effluent flow to 30 ml per minute. Use a stop watch a measuring cup, or preferably a graduated cylinder.
Now that everything is humming along, you need to wait. You will want to measure the PH of the effluent over the next few hours. If the PH of the effluent doesn't drop to below 6.9 in 4 hours or so, you will want to increase the BPM (bubbles per minute), and recheck in two hours -repeating if necessary.
MAKING ADJUSTMENTS
Let the reactor run for 24 hours or so, then perform alkalinity and calcium tests. If your tests give you the same results as when you set up the reactor congratulations, your all set. More often than not you will need to make adjustments.
As a note, use your alkalinity test to decide what adjustments to make. Alkalinity is used much quicker than calcium and will give you a better read on what you need to do. Your calcium will follow alkalinity so don't worry about adjusting for it.
If your alkalinity is low, lower the PH of your effluent by increasing the BPM. By adding more carbon dioxide and lowering the PH you will cause more of the media to dissolve thereby increasing the amount of calcium and alkalinity in the effluent. You want to make sure that you don't drop the PH below 6.5 as this could cause the media to dissolve into a mush (NOTE: as indicated in a post by Cali-Reef some coarse media types require a PH close to 6.3) and it will not be as effective. If you start to reach 6.5, instead of increasing the BPM you will want to increase the effluent rate.
If your alkalinity is higher than when you started, the reverse it true. Back off on either the BPM or the effluent rate. You will need to disconnect the calcium reactor until the levels come back down. If you adjust the reactor so that the levels fall slowly, you will need to readjust the reactor again when you hit your target levels.
It is better to set the calcium reactor to keep your levels constant and then either disconnect the reactor or add supplements to bring your tank level in line with your target levels. DO NOT USE THE REACTOR TO MAKE ADJUSTMENTS.
A COMMON PROBLEM
A common problem that people run into is that the PH in their aquarium drops to undesirable levels due to the addition of the low PH effluent. There are two a couple of things you can do. Have the effluent discharge into a high flow, turbulent area of you sump so that the effluent has an opportunity to off gas before returning to your display tank. I have the effluent drip into my skimmer, which serves the same purpose. You could also cut back on the BPM, i.e. raise the PH of the effluent, and adjust for this by increasing the effluent flow. Finally some people don't run the reactor at night when the PH of their tank is already naturally low.
If you have an appropriately sized calcium reactor you should not have a need for the addition of two part or using Kalkwasser (i.e. pickling lime). That being said, there are many people who use a "kalk stirrer" in conjunction with a "calcium reactor". This is done to offset the potential PH drop caused by a calcium reactor, as water saturated with kalkwasser has a very high PH. Note that Klakwasser is also a balanced two part additive and will therefore decrease the amount of calcium and alkalinity you need to add via the calcium reactor.
Hope that helps...
Please note that these recommendations are designed to get you up and running. You will find in time that you get a "feel" for what is going on, and like everything it will become second nature.
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