CO2, pH, and temperature controller

The reading is only valid if the electrode is immersed in water that is representative of the tank. Never place it above your diffuser, as the bubbles create a highly acidic zone right around the glass: the unit reads a pH already at the target whilst the rest of the tank is not, and it cuts the gas off too early. Position it upstream of the injection point, in a well-circulated, dark area, for example near the filter intake strainer, using the suction cups supplied with the probe. Submerge it no more than 2/3 of its length, cap and cable out of the water, and keep its cable away from electrical cables. The 2 suction cups supplied with the controller are used to hold the temperature probe, which can be placed anywhere in the tank.

On first switch-on, the unit prompts you to select a language, then requires a two-point calibration before any other setting can be adjusted. Both probes, pH and temperature, are immersed together in each solution: first the pH 7.00 buffer, then the pH 4.00 buffer, never the other way round. The unit allows up to one and a half minutes per buffer for the signal to stabilise. The calibration reminder is factory-set to 30 days and can be extended to 45 or 60 days, though the latter is not recommended. Once the interval has elapsed, the unit continues to regulate, but the alarm will only clear after a fresh calibration. The messages DELTAV, OFFSET and UNSTAB indicate, respectively, a slope that is too low, an offset zero and an unstable signal, usually a probe that needs cleaning or replacing.

A technical substrate releases acidity during its first few weeks. If you connect the controller straight away, it reads a pH already below the set point and either never opens the gas valve, or opens it in fits and starts. Allow the tank to stabilise, carry out your water changes, and start the regulation once the pH no longer shifts from one day to the next. The first weeks of a new setup are for biological cycling, which a gas injection will not speed up. The same caution applies after a large water change or a filter clean: wait 1 or 2 days for the reading to return to its normal level before relying on the regulation.

In a system where fish, bacteria, and plants share the same water, pH is the result of a constant compromise: above 7, iron and manganese become less available to plants, while below that level, the biofilter bacteria slow down. A continuous-monitoring controller reveals the gradual drift that manual testing misses. The topic is covered in depth in regulating the pH of an aquaponic system, and can be verified by hand with a pocket tester once a week. A fish tank connected to growing beds will also see its pH drop naturally over the weeks, as nitrification consumes alkalinity. The controller reveals this drop but cannot correct it: if the set point is reached without the gas valve ever opening, your water is acidifying on its own and the KH is falling.

The unit also works in saltwater, on a calcium reactor. This reactor dissolves the limestone of a grow medium, coral rubble, for example, to restore to the aquarium the carbonate hardness that its inhabitants consume, and for this it requires a pH of around 6.5, maintained continuously by CO2 injection. Fit the probe in the designated port on the reactor, or in the outflow, set the target to 6.5 and connect the solenoid valve to the CO2 supply feeding the reactor. Natural seawater contains, as a reference, between 6 and 9 °dKH depending on the region.

You receive the touch-screen unit, its digital temperature probe and 2 suction cups, the wall-mounting rail with 2 screws and 2 wall plugs, the solenoid valve connection cable, the 12 V power supply and a test tube rack for calibration. The pH probe and the solenoid valve are ordered separately, which means you can keep the controller when the electrode reaches the end of its life. The unit controls the JBL ProFlora CO2 Valve, or any CO2 system fitted with one, and this is what you need to plan for on your cylinder.

First fix the rail horizontally on the wall, close to the tank, using the two screws supplied, then hang the unit from the top and click it into place with a gentle push; it releases by sliding it sideways. Unroll the solenoid valve cable before drilling, as its length determines the distance between the display and the bottle. The unit is for indoor use only, in a dry location protected from frost, and its settings are retained in the event of a power cut.