Setting up a Calcium reactor via a Ph Controller | D-D The Aquarium Solution

The ph needed to 'melt' the media will depend on the media used , typically

though an internal reactor Ph of between 6.1 - 6.5 will be required.

There are two key reactor settings that will need adjusting to tune the reactor

and to maintain your systems demand for Calcium and Alkalinity.

When setting up the reactor you will only need to test the effluent for Alkalinity

as the reactor will produce Alkalinity and Calcium in balance. Therefore

there is no need to check the effluent for Calcium if the reactor is producing

the required levels of Alkalinity.

Effluent rate:

To tune the reactor for best performance you first need to set the effluent

rate. I suggest starting out with a slow drip rate of around 1 drop every

two seconds (30 drops a minute) .Once the reactor is set up this can be

increased to match the demand of the tank. If using a fixed peristaltic pump

ensure that it is rated correctly for the reactor .

If the peristaltic pump specified or effluent output rate is set higher than

the maximum working capacity of the calcium reactor you will find that the

effluent Alkalinity (dkh ) will drop even if setting a very low Ph within

the reactor or high bubble rate. This is due to the contact time within the

reactor being too short for the capacity of media it can hold.

Internal Ph/bubble rate:

Once the initial effluent rate has been set we need to look at the CO2

bubble rate and if using a Ph controller the internal Ph of the reactor.

 If using a feed pump/variable drip rate set CO2 rate at a count of around twice

that of the effluent drip rate, after leaving the reactor running for at

least an hour check the effluent Alkalinity using an aquarium test kit

(Salifert kit in low range mode is quite accurate). You are aiming for an

effluent dkh of between 35-50dkh, if the effluent dkh is low increase the

bubble rate slightly and test an hour later. Continue to do this until the

target dkh is reached. This will be the optimum output for the reactor at the

drip rate set.

If using a ph controller then set this initially to switch the C02 supply

solenoid off at a ph of 6.5, adjust the CO2 bubble count to around 30

bubbles per minute to begin with. Leave this for two hours then check the controller

display, the ph inside the reactor should have dropped down to the desired ph i.e.

6.5. If you find the ph has not dropped sufficiently slowly increase the

bubble rate leaving an hour between each adjustment until the Ph has dropped

to that set on the controller.

Calcium reactors work best with a steady constant supply of CO2 so don't be

tempted to crank up the bubble rate to reduce the ph quickly, this will

result in the solenoid cycling on and off over short periods and possibly

causing excess CO2 to build up in the reactor.

Once the desired Ph has been reached check the effluent Alkalinity, the

ideal Alkalinity should be between 35-50dkh. If the effluent Alkalinity is

low drop the controllers Ph by 0.1 and leave for an hour and check the

effluent dkh again. You may find you have to increase the bubble rate with

each adjustment of the controller to achieve the new Ph limit set, this is


When you find the effluent dkh is between 35-50dkh your controller will be

set at the correct Ph required to 'melt' your media. Remember to calibrate

your Ph probe before set up!!!

Final adjustments:

Once the reactor has been set up to achieve the optimum effluent alkalinity

you will need to tune the reactor for system demand. With the reactor

running check your systems alkalinity, write down the results and check the

systems alkalinity again 24 hours later. If your systems alkalinity has

dropped you will need to increase the output of the reactor to match demand.

If using a feed pump adjust the effluent rate via the red control tap on the

reactor ,you should aim to increase the output by around 25% from the base

setting above. After an hour test the effluent dkh, if you find that

effluent dkh has dropped increase the bubble rate to achieve the correct

effluent dkh.

Check the aquarium alkalinity again 24 hours later and if

needed follow the steps above to increase the reactors output again. Repeat

these steps until you find the aquariums Alkalinity and Calcium demands are

being met by the reactor

If using a fixed peristaltic pump you can attempt to increase the reactors

output dkh into its upper levels by increasing the bubble count, don't try and

force the effluent dkh up too high though as this may result in the Media

turning into a mush and CO2 building up in the reactor.

If using a Ph controller you may wish to reduce the ph in the reactor in an

attempt push up the effluent dkh, an internal ph of under 6.1 may result in

gas building with the reactor and the media breaking down and

becoming dusty.

Its important to test the Aquariums alkalinity 24 hours after any adjustment

so demand can monitored and the reactor adjusted to suit as above

It is advisable to only run the CO2 via a solenoid during the day and turn

it off during the night, this is because the effluent from the reactor has a

low Ph.

During the day your aquarium ph will be higher due to coral/algae

respiration within the aquarium. At night the Ph will drop naturally and the

reactor effluent may pull the aquarium Ph down even further to undesirable

levels, so depending on the Ph stability of your system you may want to turn

the CO2 off during the night and run it slightly harder during the day.

Monitor the Ph swing of the aquarium and if the Ph swings by more than

0.2-0.3 during a 24 hour period it would be advisable to only run the

Calcium reactor CO2 supply during the day.

 As an extra measure the use of a Kalkwasser stirrer that is set to dose

during the night will help stabilise Ph and add  Calcium and Alkalinity

to the system.


Key points:

If you make adjustments to increase the effluent rates you will need to make

appropriate adjustments to the CO2 rate to maintain effluent alkalinity

Set the internal Ph of the reactor to give the desired effluent Alkalinity,

this will be the optimum Ph for your media

Set the effluent flow rate and effluent dkh to keep up with system demand,

if the system Alkalinity increases then decrease the effluent amount and/or

the effluent dkh via the bubble count (internal reactor Ph) and visa versa.

Always specify the correct size calcium reactor for the aquarium, when you

reach the maximum effluent rate for the reactor the effluent dkh will drop

regardless of Ph or CO2 input. Its better to over spec a reactor and run it

at half duty if needs be than choose one that’s too small and struggle with it.

Decrease the on time of the C02 solenoid via a timer if you wish to turn off

the CO2 supply at night to reduce Ph swings.

Adjust the CO2 count as low as possible to achieve the desired reactor Ph if

using a controller to prevent frequent on/off cycling of the solenoid

Leave at least an hour after adjusting the reactor to test effluent dkh

Don't attempt to throttle the effluent back via the red control tap if using

a Peristaltic pump, this will damage the pump. Keep the tap open at all


Always leave the reactor feed pump and recirc pump running.

Make sure all CO2 fittings aren't leaking and a non return valve is in place

to stop tank water entering the solenoid.