EcoTech Marine makes one dosing pump for reef aquariums: the VDM (Variable Dosing Module). It's a two-channel peristaltic dosing system that integrates directly with the Apex controller (via the EcoTech ReefLink module) and with EcoTech's Mobius app for standalone wireless control. If you're running an EcoTech-centric setup with Vectra return pumps and Radion lights, the VDM fits naturally into that ecosystem. If you're not already invested in EcoTech or Apex, there are comparable dosing pumps available for less money that work just as well mechanically.

This guide covers what the EcoTech VDM does, how it compares to alternatives like the Neptune DOS and Kamoer FX-STP2, how to set it up for two-part dosing, and what the Mobius ecosystem integration adds in practice.

What the EcoTech VDM Is (And Isn't)

The EcoTech VDM is a two-head peristaltic dosing pump. It doses calcium and alkalinity solutions (or any two liquid supplements) from separate containers through independent channels. EcoTech positions it as a companion to their other equipment, and the ecosystem integration is the main differentiator.

What it is: - A two-channel peristaltic pump with precise dosing capability (doses as small as 0.25 mL) - Mobius app-connected with scheduling, logging, and remote control - Compatible with Apex controller integration via EcoTech ReefLink - Built to EcoTech's typical quality standards (solid, reliable, US-designed)

What it isn't: - A four-head doser (you get two channels, period) - A standalone alkalinity controller (you still need to test and adjust manually unless you pair it with a third-party alkalinity probe system) - Cheap (it runs $150-200, more than comparable mechanical alternatives)

If you need more than two dosing channels, you'd need a second VDM or a different pump entirely. For complex dosing regimens that include magnesium, trace elements, amino acids, and two-part, the VDM's two-channel limitation becomes relevant.

EcoTech VDM Setup

Setup takes about 30-45 minutes, including app configuration.

Physical Installation

Mount the VDM near your sump using the included bracket or set it on a flat surface inside your aquarium cabinet. Run the intake tubes down into your dosing solution containers (sold separately; any clean container with a cap works for holding solutions). Run the outlet tubes into your sump.

The pump heads prime by running in reverse briefly to draw solution into the tubes, then confirm by running forward. EcoTech's Mobius app guides you through the prime sequence step by step.

Mobius App Connection

The VDM connects to Wi-Fi (2.4GHz) through the Mobius app. If you have other EcoTech devices, they all appear in the same app view, which is convenient. Setup involves scanning the QR code on the unit and following the app's connection wizard. Most users complete this in under 10 minutes.

Calibration

Calibrate each channel using the app's calibration function. The app prompts you to run the pump for a set number of cycles, measure the actual output volume with a syringe, and enter the measured volume. The app then calculates the correct scaling factor for that channel.

Recalibrate every 3-4 months as peristaltic tubing wears. EcoTech replacement tubing kits are available and recommended annually.

Programming a Two-Part Dosing Schedule

For a 100-150 gallon mixed reef:

Start by establishing your tank's calcium and alkalinity consumption. Test both parameters Monday and Thursday without dosing in between. The drop over 72 hours tells you daily consumption. A typical 100-gallon mixed reef consumes 15-40 mL/day of each two-part component.

Setting Up the Schedule in Mobius

The Mobius app lets you set: - Start time: When the first dose fires - Dose volume: mL per dose event - Frequency: Number of doses per day or time interval between doses

For best results, split daily doses into 6-12 smaller doses spread evenly throughout the day. If your tank needs 30 mL/day of alkalinity, program 10 doses of 3 mL each, every 2.4 hours. Smaller, more frequent doses keep alkalinity variation under 0.3-0.5 dKH between doses, which SPS corals respond positively to.

For comparisons with other reef dosing equipment, our Best Dosing Pump for Reef Tank guide covers the main options in detail.

If you're running an Apex controller, the VDM integrates through EcoTech's ReefLink module, which acts as a Wi-Fi bridge between EcoTech equipment and the Apex ecosystem.

With Apex integration, you can: - Trigger conditional dosing based on pH or ORP readings from Apex probes - Log VDM dosing activity alongside other Apex data - Create fusion rules that modify dosing output based on controller parameters

The most useful application is pH-triggered dosing: if your calcium reactor is offline or your tank pH drops below a threshold, the Apex can increase the VDM dosing rate to compensate. This level of automation is the main reason to pay the premium for VDM over a simpler standalone doser.

Without the ReefLink and Apex, the VDM operates as a standalone Wi-Fi connected doser through Mobius only, which is fully functional but doesn't provide the conditional automation.

How the VDM Compares to Alternatives

Neptune DOS (Dual Optical Sensor)

The Neptune DOS is the natural competitor if you're in the Apex ecosystem. It integrates directly with Apex without needing ReefLink, and it has optical flow sensors that verify each dose actually delivered. This optical sensing is a real advantage: if a tube clogs or runs dry, the DOS detects the absence of flow and alerts you. The VDM doesn't have this flow verification.

The Neptune DOS costs $200-250. If you're already running Apex, it's the better integration choice.

Kamoer FX-STP2

The Kamoer FX-STP2 is a 4-head doser with Wi-Fi and app control that runs $80-110. Mechanically comparable to the VDM, without the EcoTech ecosystem integration. If you need four channels and don't need EcoTech integration, the Kamoer delivers more dosing capacity per dollar.

IceCap 2K Doser

The IceCap 2K Doser runs around $100-120 for 4 channels. Good reliability, straightforward app, no ecosystem integration. For hobbyists who aren't invested in any particular controller ecosystem, the IceCap is a pragmatic choice.

Reef Factory Dosing Pump

The Reef Factory pump is a strong alternative for those considering the Reef Factory KH Keeper automated alkalinity system. The Reef Factory ecosystem's closed-loop alkalinity control (measure with KH Keeper, dose automatically with the pump) is more sophisticated than anything currently available through EcoTech's ecosystem.

See our Best Aquarium Dosing Pump guide for a full side-by-side breakdown.

Is the VDM Worth the Price?

The honest answer depends on your existing equipment.

If you're already in the EcoTech + Apex ecosystem: The VDM at $150-200 makes sense. The Mobius integration, ReefLink compatibility, and EcoTech's track record for support and firmware updates are worth the premium over a generic doser.

If you're not in either ecosystem: The VDM costs significantly more than functional alternatives that dose just as precisely. A Kamoer or IceCap pump gives you the same calcium and alkalinity stability for $80-120 less.

If you need more than two channels: Look elsewhere. The two-channel limitation is a real constraint for reef tanks where you're dosing calcium, alkalinity, magnesium, and trace elements separately.

The VDM is a well-made, well-supported product. Its value is ecosystem-dependent.

Common Issues and Troubleshooting

Inconsistent dose volumes: Tube wear is the most common cause. Run a calibration check. If one channel is delivering 10%+ more than the programmed volume, replace that pump head's tubing.

Mobius app not connecting: Confirm your network is 2.4GHz. If the VDM isn't appearing in the app, try the reset process (hold the button on the unit until the light flashes) and re-pair. Firmware updates through the app resolve most persistent connectivity issues.

Air bubbles in the dosing line: Causes missed doses because the pump pushes air instead of solution. Check that the intake tube is fully submerged in your container and that the container isn't nearly empty. Re-prime the affected channel.

Container running empty unexpectedly: Either consumption increased (common in growing coral reefs), the pump is over-dosing (check calibration), or there's a tube leak somewhere. Inspect tube connections at both the container and the sump outlet.

FAQ

Does the EcoTech VDM work without Apex? Yes. The VDM operates fully as a standalone Wi-Fi dosing pump through the Mobius app without any Apex hardware. Apex integration is an optional enhancement, not a requirement. The Mobius app handles scheduling, logging, and remote control independently.

How many heads does the EcoTech VDM have? Two channels. One for each solution (typically calcium and alkalinity in standard two-part dosing). If you need to dose magnesium or additional supplements simultaneously, you would need a second VDM or a different pump with more channels.

Can I use the VDM to dose kalkwasser? Kalkwasser (calcium hydroxide solution) is caustic and requires careful handling. Peristaltic dosing of kalkwasser is possible but typically done through a dedicated kalkwasser reactor or a drip system rather than a peristaltic pump, because precipitation can occur inside the pump head if small amounts of CO2 get into the solution. Most reef keepers using kalkwasser use a separate Kalk reactor with a dedicated peristaltic pump or gravity drip rather than the VDM.

How long do the VDM pump heads last? EcoTech recommends inspecting pump tubing every 6 months and replacing annually. Under typical use (2-4 doses per day per channel), tubing lasts 12-18 months before calibration drift exceeds 5%. EcoTech sells replacement tube sets for around $15-20 per kit, which covers both channels.

Conclusion

The EcoTech VDM is a solid two-channel dosing pump that earns its price specifically within an EcoTech or Apex ecosystem. The Mobius integration is clean, the dosing precision is reliable after calibration, and the build quality matches EcoTech's reputation. For non-EcoTech users who need two channels and basic Wi-Fi scheduling, consider the Kamoer FX-STP2 at roughly half the price before committing to the VDM. For Apex users, compare the VDM against the Neptune DOS's optical flow sensing feature before deciding. Either way, split your daily dose into 8-12 small increments, calibrate quarterly, and your calcium and alkalinity will stay stable with minimal intervention.