Water changes are one of the most important things you can do for a healthy reef tank, but they are also one of the easiest tasks to put off. They help export nutrients, replenish some trace elements, and remove undetected contaminants that can build up over time. The problem is that traditional water changes can be messy, time consuming, and easy to skip when life gets busy.

By using a Neptune Systems DOS or DOS QuietDrive, you can automate small, consistent water changes that happen throughout the day with very little effort from you. More stable water chemistry, fewer maintenance headaches, and a routine you'll actually stick to are all things we can get behind.

In this guide, we'll walk through how to set up a Neptune Systems DOS QuietDrive (QD) for automatic water changes using Apex Fusion. The setup process is exactly the same for both the original DOS and the DOS QD, so whichever version you have, you're in the right place!

What You Need to Get Started

Required Components

Neptune Systems Apex Controller
Neptune Systems Apex Controller
The brains of the operation, providing control, scheduling, and safety fallback logic to other Apex devices like the DOS.
DOS QuietDrive
DOS QuietDrive
Adds clean saltwater to your aquarium while simultaneously removing dirty water, keeping water level stable during the auto water change.
Clean and Dirty Saltwater Reservoirs
Clean/Dirty Saltwater Reservoirs
A place to store clean saltwater and collect dirty tank water. Alternatively, you can route the waste line to a drain, which is our preferred setup method.

Compatibility Note: DOS is compatible with all A1 through current A3 series Apex controllers. DOS QD is compatible with A2 and A3 series Apex controllers.

Optional Accessories

There are a few additional things that can make setup easier and safer long-term:

Magnetic Tube Holder
Magnetic Tube Holder
Keeps the AWC tubing neatly organized and properly submerged in the clean saltwater reservoir and/or aquarium/sump.
Acrylic Rod DIY
Acrylic Rod DIY
Inexpensive DIY alternative to the magnetic tube holder. Cable tie your tubing to the acrylic rod to help keep it in place.
Water Sample Filter
Water Sample Filter
A nifty pre-filter you can install on the end of your dirty water tube to stop debris from getting sucked up, reducing the chance of a clog.

Preparing Your Setup for Automatic Water Changes

Step 1: Calibrate Your DOS Pump Heads

Calibration ensures that your DOS is removing and adding the same amount of water simultaneously and helps prevent gradual salinity swings over time.

Just hit the "Tasks" icon in Apex Fusion (clipboard icon) and click the "DOS Calibration" option and it'll walk you through it all.

Step 2: Set Up Your Clean/Dirty Water Reservoirs

The DOS will need a source of clean saltwater and somewhere to put the dirty tank water.

Clean Water Reservoir: Depending on the volume of your water changes, you could use a 5 gallon bucket, Brute trash can, or a larger polyethylene water storage tank.

Dirty Water Reservoir: Use a dirty water reservoir that is at least the size of your clean water reservoir, or larger. If you have access to a drain, that's even better. We like to run the dirty water tube right to a utility sink to save on space and lessen maintenance as we won't have a dirty water reservoir to empty later.

Tip: Consider using float switches connected to your Apex so that the Apex can stop AWC if your clean water reservoir is empty or if your dirty water reservoir is full.

Step 3: Run the Tubing To and From the DOS

When you're done, you'll have four runs of tubing that look something like this:

DOS QuietDrive automatic water change tubing setup

Tip: Label the tubing near the DOS head so you can easily tell which tube should go where. This is especially helpful later when you're swapping dosing heads or doing other maintenance.

Left DOS Head: Clean Water

  • Run tubing from your clean saltwater reservoir to the left fitting on the left DOS head.
  • Run tubing from the right fitting on the left DOS head to your aquarium or sump.
Tip: Secure the output tube above the water line and make sure the tubing is secure in the clean water reservoir using an acrylic rod or magnetic tube holder.

Right DOS Head: Dirty Water

  • Run tubing from your aquarium or sump to the left fitting on the right DOS head.
  • Run tubing from the right fitting on the right DOS head to your wastewater container or drain.
Tip: Place the intake tube in a low-debris area of your sump to reduce the chance of clogs over time. Use a magnetic tube holder and/or sample water filter for a secure setup.

IMPORTANT: The DOS heads spin in a different direction when in AWC mode, so make sure you follow the setup outlined above for AWC as it is different from how we'd set up the DOS for additive dosing.

Step 4: Fill Your Clean Saltwater Reservoir

Mix up a batch of saltwater in your clean saltwater reservoir. Because we're changing such a small amount of water at a time, a heater usually isn't necessary, but having a small circulation pump at the bottom of the reservoir can be helpful for making sure the salt is mixed thoroughly.

Setting It Up In Apex Fusion

Apex Fusion DOS Automatic Water Change task screen

Step 1: Start the DOS AWC Task

In the Apex Fusion app, click on the "Tasks" icon (clipboard) and click the "DOS Automatic Water Change" option.

You'll first see a tubing diagram. Take a moment to double check that you've connected the tubing correctly.

Assuming you've completed the previous setup preparation steps and your clean saltwater reservoir is filled, press the "Next" button.

Select DOS pump in Apex Fusion

Step 2: Select Your DOS

If you have multiple DOS pumps, you'll want to make sure you select the right one. Click on it and it'll move you to the next step.

Rename DOS pump heads in Apex Fusion

Step 3 & 4: Rename Your DOS Pump Heads

First, you'll be prompted to rename the left pump head.

Next, you'll be prompted to rename the right pump head.

Tip: We like to name the left pump head "DOS_ADD" and the right pump head "DOS_REMOVE" for easy identification later.
Set daily water change volume in Apex Fusion

Step 5: Select Daily Water Change Volume

Here, you'll enter:

  • Units of Measure
  • Volume You Want Changed Daily
  • Start/End Time for Each Day's Automatic Water Change
Tip: The original DOS can be noisy during AWC, so consider scheduling the start/end time for when you're not home.
Review and send DOS automatic water change setup

Step 6: Review Setup & Prime the Lines

This step in the DOS AWC setup task is simply a recap of the information you've entered.

Make sure everything looks correct, then click "Send" to officially configure the DOS for AWC.

Prime the Lines

Hold the "L" button on the DOS to prime the clean water line. Keep holding this button until water starts dripping into your tank or sump.

You don't necessarily need to prime the waste side dosing head, but you can do so to inspect for any leaks or unexpected issues.

Tip: It can be tempting to go into Apex Fusion and turn the dosing heads to "ON" to prime the lines, but we don't recommend it.

 

Frequently Asked Questions

What is an Automatic Water Change (AWC)?

When using a dosing pump as an automatic water change system, water is removed and added to the tank or sump at the same time, so there is no change to the water level. In reality, it's more like a water exchange.

It's usually set up to remove smaller amounts of water throughout the day vs a single big water change once a week or once a month that we'd do manually. These smaller, but more frequent water changes have the added benefit of helping to maintain stable water chemistry, reducing the see-saw spikes and valleys of water parameters.

What is the Neptune Systems DOS?

For those that are just starting the research phase of looking into automatic water change systems, the DOS is a dual-head dosing pump for the Neptune Systems Apex aquarium controller.

It's most often used for precisely dosing additives like calcium and alkalinity, but has become extremely popular for AWC setups in the last few years thanks to easy setup in Apex Fusion and integration with the Apex controller ecosystem.

DOS vs. DOS QuietDrive (QD): What's the Difference?

The steps in this guide will apply to both the DOS and DOS QD; setup is exactly the same.

The QuietDrive version is the newer of the two and utilizes technology first seen in EcoTech Marine devices that makes the QD significantly quieter. This is a welcome upgrade when it comes to AWC setups as the dosing heads are moving quickly and generally produce more noise vs lower-volume two-part dosing.

How Often Will I Need to Change the DOS Dosing Heads?

How often you'll need to swap out the dosing heads will be highly dependent on how volume they're moving.

Because we don't want to be changing these out after a failure, a good rule of thumb would be to replace them about once per year when using the DOS for automatic water changes. For lower volume additive dosing, the pump head lifespan is significantly longer.

How Often Will I Need to Refill the Clean Saltwater Reservoir?

This depends on the size of the reservoir and water change volume.

We usually like to use a reservoir that can hold about a month's worth of clean saltwater.

Do I Need to Heat the Water for My Automatic Water Changes?

Typically, no.

Because the DOS is adding and removing small amounts of water over the course of many hours, room-temperature saltwater won't cause a noticeable temperature drop in your aquarium.

Can I Use Standard RO Tubing Instead of the Provided DOS Tubing?

Yes!

This is actually how we have most of our DOS AWC systems set up here. It's a tight fit, but you can push standard 1/4" RO tubing onto the DOS heads with some gentle force.

Alternatively, you can use a 1/8" female thread x 1/4" push connect adapter to convert your DOS to accept 1/4" RO tubing more easily.