This is Part 2 in a two-part series. Miss Part 1? Click here.

A calcium reactor is a great way to maintain calcium and alkalinity levels for aquariums with high demands. Today we are going to explain how to properly dial in your calcium reactor.

Before getting into the nitty-gritty, you should know that each calcium reactor is different and the actual setup may vary. This article and the accompanying video are intended to be a general guideline to show you the key points and provide helpful tips that will help you get your reactor operating properly.

After assembling your reactor and getting the tubing connected, you want to find a secure place to mount the reactor. The reactor can be mounted above or below the water level in your aquarium when using a feed pump. Just be sure you have enough room for the CO2 tank and reactor. The outlet tubing needs to be attached to your sump or aquarium with the end of the tubing above the water level and the adjustment valve wide open for the time being.

Next, turn on the feed pump to start filling the reactor with aquarium water. Be sure the CO2 gas and recirculation pump on your reactor are turned off. Because your reactor is taking water from the aquarium, you will probably need a couple of gallons of extra saltwater on hand to fill up the tank after the reactor is full. It is best to have the feed pump pull water from a calm area of the aquarium to avoid air bubbles from entering the reactor.

Once the reactor is full, water will start pouring back into your tank via the outlet tubing and it is then safe to turn on the recirculation pump on your reactor. Allow the reactor to run for a few hours without injecting any CO2. This will help remove any air bubbles and allow the calcium reactor media to become saturated with saltwater to force out trapped air. Check closely for any water leaks and ensure air is not entering the reactor from your feed pump.

Once all the air has escaped and your reactor is being fed properly with aquarium water, you can set the outlet drip rate. The exact drip rate varies, so follow the manufacturer instructions—we typically recommend 40-60 drops per minute to start. Slowly open up your CO2 regulator to start injecting CO2 into the reactor. Be sure the solenoid valve is plugged in and use the adjustment valve on your regulator to adjust the output of CO2 to be about 10 x CO2 bubbles per minute (about one every 6 seconds).

Allow the calcium reactor to run and break in for a few days at these initial settings. Watch the pH in your aquarium to ensure it is not dropping to dangerous levels and test your calcium and alkalinity every day and record it. Be sure your calcium, alkalinity and magnesium levels are balanced before turning on the reactor. This will make it much easier to see the effects of your calcium reactor and dial it in correctly. It is really important to remember while setting up your reactor that you need to make very small changes and allow time for the changes to take effect.

After a few days, you will need to check the effluent (or outlet water) that is dripping back into your tank with a with a pH test kit, a pH monitor or a pH controller. Most modern calcium reactors have a pH probe port on the reactor itself, which makes things easier, although you can also use a drip cup or just collect some of the water before it enters your tank. Your target effluent pH level is between 6.5 and 6.7. If the pH is too high, you will need to either increase the CO2 bubbling rate by two or three bubbles or decrease the effluent drip rate by 5-10 drops. If the pH is too low, increase the drip rate or cut back on CO2.

After making changes, allow the reactor to run for a day. Then test the effluent pH again before making further changes. A pH controller like the Pinpoint pH Controller, Neptune Systems Apex AquaController or the Digital Aquatics Reefkeeper can be very helpful in operating the CO2. You simply set the controller to only allow enough CO2 to keep your pH within range. It will control the CO2 injection by turning the CO2 regulator's solenoid on and off based on the pH target range you set.

Initially, you will need to test your aquarium daily to see if your alkalinity and calcium levels stay the same, increase or decrease from day to day. We highly recommend keeping a log of your test results.

After about a week of daily testing, you should be able to tell if you need to add more or cut back. If you need more calcium/alkalinity from your calcium reactor, increase your effluent drip rate ever-so-slightly. Keep an eye on the effluent pH to ensure it stays within the 6.5 to 6.7 range.If the effluent pH rises out of range after increasing your drip rate, simply bump up your CO2 rate.

If the reactor is adding too much calcium/alkalinity into your aquarium, decrease your effluent drip rate. It is likely you will also need to decrease the CO2 injection rate. As mentioned earlier, make small changes and allow time for the changes to take effect before making further adjustments. Injecting too much CO2 will cause the media to melt or create a pocket of CO2 gas in your reactor which would then require you to start all over.

Continue with daily testing until you are confident the reactor is supplying your tank with the calcium and alkalinity levels needed. It is a balancing act that will require regular testing and small adjustments until it is operating smoothing. We recommend checking on the reactor and your calcium and alkalinity levels every week or two thereafter. You only need to refill your CO2 cylinder after several months of use and replace the reactor media about once a year. If you added Magnesium media to the reactor, be sure to test regularly so you'll know when to add more. If you did not, you can use a magnesium supplement to keep your levels where they should be.

You may occasionally need to make larger adjustments to your calcium or alkalinity levels. We recommend using an alkalinity buffer or a calcium supplement. A calcium reactor is intended to maintain your current levels, not make large increases. If you try to use the reactor to boost your levels, you may cause large pH swings, which are dangerous to your aquarium and can possibly melt your media, forcing you to start all over again.

Calcium reactors are one of the more complex pieces of reef aquarium equipment. But with a little understanding and the willingness to give it the attention it needs to get up and running, a reactor can really save you time and money—not to mention help you grow breathtaking coral colonies.

If you found this article and/or the accompanying video helpful, please "like" and share them with your reef keeping buds considering a calcium reactor. Don't forget to subscribe to our YouTube channel so you can stay up-to-date on the latest hobby news and get expert advice from our staff.

If you have questions, leave us a comment below or contact us because we'd be happy to help you out. Until next time... take care and happy reef keeping!

This is Part 2 in a two-part series. Miss Part 1? Click here.

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