GHL Doser 2 Setup Guide: Calibration and Schedule
The GHL Doser 2 SA looks deceptively simple in its slim aluminium chassis, but its accuracy depends on a calibration routine most people skip on day one. A proper GHL Doser 2 setup guide walks through tubing prep, head priming, ml-per-second calibration and the schedule logic that keeps a reef tank stable for months. This guide from Gensou Aquascaping at 5 Everton Park reflects three years of running multiple Doser 2 units across SPS systems, including how to integrate them with the rest of your control loop. Singapore reefers will find the supply line and electrical notes especially useful.
Unboxing and What You Actually Need
The standalone unit ships with four pump heads, four lengths of soft silicone tubing, suction tube weights and a power brick. You will need to source dosing reservoirs separately along with PE or PVC stiff tubing for the run from container to pump intake. Budget another $40 SGD for proper anti-siphon valves; the included weights alone are not enough to stop back-siphon during power cuts.
Mounting and Cable Routing
Mount the Doser 2 above the reservoirs and at least 30 cm above the maximum waterline of your sump. Gravity assists priming and prevents the heads working against pressure. Route the power cable through a drip loop and secure tubing with cable ties every 25 cm so vibration does not loosen joints over time.
Tubing Preparation
Cut the supplied silicone with a sharp blade rather than scissors so the ends remain perfectly round. A slightly oval cut leaks at the barb fitting after a few weeks. For two-part calcium and alkalinity, use separate tubing colours or label tape to avoid mixing up reservoirs during refills. Soak new tubing in RODI for 30 minutes before connecting; this removes manufacturing residue that otherwise discolours your dose.
Initial Priming
Run each head in manual mode at 100% until liquid emerges from the discharge end, then run for another 10 seconds to clear bubbles. Bubbles trapped in the head reduce dose accuracy by up to 8% and confuse later calibration. The pump motors are quiet but produce a faint click per peristaltic rotation; this is normal and not a sign of wear.
Calibration Procedure
Place a graduated cylinder under the discharge tubing and run the calibration routine via myGHL or the local control panel. The unit will dispense for 60 seconds at full speed; record the actual volume to the nearest 0.5 ml and enter it. Repeat for each head individually because tolerances vary up to 5% between heads from the factory. Re-calibrate every six months as silicone tubing softens and dose volume drifts.
Setting Up Schedules
Split the daily alkalinity dose across at least 24 small events rather than one large dump, ideally 48 if you run heavy SPS. Stagger calcium and alkalinity dosing by at least 30 minutes to avoid local precipitation in the sump. Magnesium can run as four daily doses without the same precipitation risk. The patterns described in our two part dosing guide reef tank walkthrough apply directly to GHL.
Pairing With Slave Units
Adding a Doser 2.1 SA Slave gives you four more heads for trace elements, amino acids or kalkwasser top-up. Pair via the GHL bus connector on the back; the master unit then exposes all eight heads in myGHL. Keep slave heads on a separate reservoir layout to avoid clutter and confusion when refilling.
Reservoir Choice and Sizing
Two-litre reagent bottles work for nano reefs but you will be refilling twice a week on a heavy SPS load. Five-litre HDPE jerry cans last a fortnight on most mid-sized systems and stack neatly in a sump cabinet. Calculate weekly demand from your tank volume and dose rate; our best reef dosing container setup piece walks through sizing.
Anti-Siphon and Safety
Power outages or a cracked head can siphon an entire reservoir into the sump within hours, crashing alkalinity dramatically. Install a check valve on each line and route the discharge tubing in a high loop above the sump rim before dropping to the dose point. The 15 minutes spent here prevents a tank disaster.
Integration With Apex or ProfiLux
The Doser 2 SA standalone can be triggered from a ProfiLux 4 controller via 1-10V or via myGHL cloud automation. Apex users typically run the Doser 2 in standalone mode and pull data via the cloud rather than direct integration, which is functional but not seamless. Local logic on the Doser handles failsafes if Wi-Fi drops, which Singapore home networks occasionally do during heavy rain.
Maintenance, Singapore Pricing and Spares
Replace silicone head tubing every 12 months on a heavy duty cycle, longer if you only run trace dosing. Inspect rollers for residue at the same interval and wipe with a damp microfibre. Re-calibrate after each tubing change. A pump head that is rattling or running hot needs immediate attention; the motors are not field-serviceable.
Expect $480-540 SGD for the Doser 2 SA from Polyart or selected Reef Builders Asia stockists. Spare tubing sets retail around $15 and slave units run $380. Genuine GHL spares ship from Germany via the local distributor, which takes 10-14 days; keep a spare tubing kit at home so you are never waiting mid-refill.
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