JBL ProFlora CO2 Control pH and CO2 regulation computer

The reading is only reliable if the electrode sits in water that is representative of the tank. Never place it above your diffuser, because the bubbles create a very acidic zone right around the glass: the device reads a pH already at the set point while the rest of the tank is not, and it cuts off the gas too early. Place it upstream of the injection, in a well-circulated, dark area, for example near the filter's intake strainer, using the suction cups supplied with the probe. Immerse it to no more than 2/3 of its length, with the cap and cable out of the water, and keep its cable away from electrical cables. The two suction cups supplied with the controller, for their part, hold the temperature probe, which can go anywhere in the tank.

When first switched on, the unit requires you to choose the language, then a two-point calibration before any other setting. The two probes, pH and temperature, are immersed together in each solution, first the pH 7.00 buffer and then the pH 4.00 buffer, never the other way round, and the unit waits at most a minute and a half per buffer for the signal to stabilise. The calibration reminder is set at the factory to 30 days, and can be changed to 45 or 60 days, the latter being not recommended. When it falls due, the unit keeps regulating, but the alarm only stops after a new calibration. The messages DELTAV, OFFSET and UNSTAB indicate respectively a slope that is too low, an offset zero and an unstable signal, often a probe that needs cleaning or replacing.

An active substrate releases acidity during its first few weeks. If you connect the controller straight away, it reads a pH already below the setpoint and never opens the gas, or opens it in fits and starts. Let the tank settle, carry out your water changes, and switch the regulation on once the pH no longer varies from one day to the next. The first weeks of a new setup are for the biological start-up, which gas injection does 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 settle again 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, and below that, the activity of the biofilter bacteria slows down. A controller that measures continuously reveals the slow drift that manual readings miss. The subject is covered in the article on regulating the pH of an aquaponic system, and this pH can be checked by hand with a pocket tester once a week. A fish tank linked to grow beds will also see its pH fall of its own accord over the weeks, because nitrification consumes alkalinity. The device reveals this drop without being able to correct it: if the set point is reached without the gas ever opening, your water is acidifying on its own and the KH is falling.

The device can also be used with seawater, on a calcium reactor. This reactor dissolves the limestone of a grow medium, crushed coral for example, to restore to the aquarium the carbonate hardness that its occupants consume, and for this it needs a pH of around 6.5, held constantly by CO2 injection. Install the probe in the port provided on the reactor, or in the water flow leaving it, set the target value to 6.5 and connect the solenoid valve to the CO2 supply feeding the reactor. As a reference, natural seawater is between 6 and 9 °dKH depending on the region.

You receive the touch-screen unit, its digital temperature probe and its 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 holder for calibration. The pH probe and the solenoid valve are ordered separately. The unit controls the JBL ProFlora CO2 Valve solenoid valve, or a CO2 system fitted with one, and this is the one you should plan for on your cylinder.

First fix the rail horizontally to the wall, near the tank, with the two screws supplied, then hang the unit from the top and click it into place with light pressure; it comes off by sliding it sideways. Unroll the solenoid valve cable before drilling, since its length determines the distance between the screen and the cylinder. The unit is for indoor use only, in a dry place protected from frost, and its settings are retained in the event of a power cut.