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Which Aquarium Controller Should I Get?

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Last updated on November 17th, 2023


Which Aquarium Controller Should I Get?

What is a Reef Tank / Aquarium Controller?

A reef tank controller, or saltwater aquarium controller, is a device (or multiple) that can both monitor parameters and turn other devices on and off. Most aquarium controllers have a controller itself and then you can buy extra add-on devices depending on what you want to control or monitor. For example, The Neptune Apex comes with a SMART energy bar, but to monitor alkalinity you will need to purchase a Neptune Trident.

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Aquarium Monitor First - Then Aquarium Control

The primary function of reef tank controllers should be monitoring the aquarium parameters. Controlling parameters and devices should be a secondary component. It's a huge benefit, but in reality, you can usually add your own chemicals or turn things on/off yourself. That's what you would do if you didn't have a controller, right? Starting with monitoring gives you a warning that something is wrong that you wouldn't have known before, then you can add control later.

Aquarium Controller - Reef Tank Monitor

I'm going to REALLY DRIVE THIS POINT HOME. If you DO NOT have a aquarium controller, what do you do? You measure your parameters daily (you should be, but we all know it's more like once a week/month...). Then you write the number down on your phone or a piece of paper (*cough cough* You should be using the Reef Stable's Parameter Log). If any parameters are "out of range", you either add something to correct this, or do a water change. Hopefully you're looking at how much the parameter changes from day-to-day and adjust according to that.

This is perfectly fine for most beginner reef tanks, or low demand tanks. Now let's say you just spent a lot of money on some high-end SPS or Torch Coral and it's dying (or dead). What happened? All of your parameters are within range according to your test this morning. Well, this is where an aquarium monitor comes in handy.

Constantly Monitoring Parameters

If you had an aquarium controller as a parameter monitor, you may have noticed in the example above what was wrong. Maybe temperature or pH drops dramatically at night. Maybe you're adding too much akalinity buffer and don't know because you only measure once a week. Or maybe you added the chemical when alkalinity/pH were at their highest and it fried the coral. All of these things can be solved with a reef tank controller as a monitor. You can see real-time numbers as well as a graph (in most cases) of your parameters throughout the day/week. Saving you time, money, and most importantly, saving your reef tank!

What Parameters You Should Monitor with a Reef Controller

Some parameters can DIRECTLY affect your coral and fish health. These parameters can affect both growth rate, as well as determine if your fish and coral will survive. While this list is in my priority order, there may be some discrepancy and you'll have to decide for yourself.


The reef tank's temperature is the most important parameter to monitor because it can lead to stress and death in reef aquarium life very quickly.


The amount of salt in your reef tank is the second most important parameter to measure. Too much or too little salt can kill coral fairly quickly. While most fish and some coral can adjust to low salinity if it is over time, quick changes can get very dangerous very fast. Additionally, salinity monitoring can tell you if an ATO is stuck on (possibly indicating either a leak or hardware failure) as well as something as simple as a protein skimmer overflowing and the ATO kicking in too long.


This is where things may be controversial. I believe that low pH, or pH swings, are a likely reason for coral deaths that are not explained by temperature, salinity, pests, or fish/inverts eating the coral. Since scientists are saying coral reef deaths are due to ocean acidification (lowering pH) then why is your reef tank any different?

According to The National Oceanic and Atmospheric Administration (NOAA) the ocean surface pH has dropped by 0.1 pH across the last ~200+ years, from 8.2 to 8.1. If the NOAA is saying that this 0.1 pH and a degree or two rise in water temperature over 200 years is the reason for massive reef die-off, yet most reef tanks are said to be "in range" and we're often told "don't chase the numbers" if pH is between 7.8 and 8.4, I think we can see how one of these must be wrong. TLDR - I would strongly encourage monitoring your pH.


Tying in to pH above, alkalinity is used to measure the potential for a change in pH when acid is present. So a less scientific way of saying it, the higher the alkalinity, the more acid (in our case, CO2) is needed to drop the pH in the reef tank. If alkalinity get's too low, your pH will drop quickly when something as simple as visitors coming over cause more CO2 from breathing in the room.

Nice to Have - But Not Required Parameters to Monitor

While not as crucial for the life or death of reef tank life, there are some other parameters that are "nice to have". Thought they're not as crucial, things like out of control Magnesium could lead to snail death. Additionally, nutrients could narrow down algae, bacteria, or dino outbreaks before they're out of control!


Calcium is a nice parameter to monitor because it helps you ensure everything is within range for your corals' needs. Calcium shouldn't sway quickly so it's not as important as the parameters above, but it's good to ensure you're not way too high or low. Honestly, testing calcium weekly is usually enough to ensure everything is okay.


Magnesium, much like calcium, shouldn't change much, nor should it change quickly. That being said, if it gets too high (above 1500 or so), it can cause snails to be unable to move, and then die of starvation.


High Nitrate levels can lead to excess algae growth in your reef tank. Low nitrates can lead to dinos as well as loss of color in coral. Additionally, changes in nitrate levels can help indicate over/under feeding or if something died in the tank and is rotting. While I personally only get around to measuring nitrates every couple months, it takes 5 minutes or less so I have no excuse. That being said, if this were automatic, every week or even every couple of days, I could get ahead of algae growth before it's a problem.


Everything I said for nitrate applies for phosphate monitoring as well! The difference is that phosphate is more dangerous to coral. It can prevent their uptake of calcium and bicarbonate preventing growth or possibly suffocating them. So again, monitoring would be ideal, but at the very least, test-test-test.

Reef Controllers

Now that we have identified what we want to monitor, what do we need to actually do so? Let's look at a few options. Let me note right off the bat, this is not a full list of ALL of the options, just some of the more popular options available.

Neptune Apex

To monitor temperature and pH with the Neptune Apex, the probes are included as part of the base packages. Most Apex Models require you to add a PM2 Module and Conductivity Probe. The pro model however included the port for salinity, but you will still need the probe.

Additionally, to add alkalinity testing with the Neptune Apex, you will need the Neptune Trident. On a positive note, this includes Calcium and Magnesium testing. Unfortunately, at this time, Neptune does not offer a way of monitoring nitrate nor phosphate.

Neptune Apex - Parameters Available

UnitSalinityTemperaturepHAlkalinityCalciumMagnesiumNitratePhosphateCurrent Price
Apex A3 Jr. Requires PM2 Module and Salinity ProbeIncludedIncludedRequires TridentRequires TridentRequires TridentNot AvailableNot Available$299.95
Apex A3Requires PM2 Module and Salinity ProbeIncludedIncludedRequires TridentRequires TridentRequires TridentNot AvailableNot Available$599.95
Apex A3 ProRequires Salinity Probe (Port Included)IncludedIncludedRequires TridentRequires TridentRequires TridentNot AvailableNot Available$899.95

Neptune Apex Price

As of writing this, the total for all of this with the Neptune A3 is roughly $1227.80 for the Apex Jr (monitoring only) or $1527.80 if you want the base model of the Neptune Apex A3. If you spring for the pro model, the salinity port is included, but you still need the conductivity probe. That combo will set you back about $1737.85.

UnitCurrent Price
Apex A3 Jr. + Trident + PM2 + Salinity Probe$1227.80
Apex A3 + Trident + PM2 + Salinity Probe$1527.80
Apex A3 Pro + Trident + Salinity Probe$1737.85

Total Cost: $1227.80 - $1737.85

Neptune Apex - Final Thoughts

Personally speaking, the Neptune Apex is the controller I use and would likely choose again. While I really want a reason to set up multiple controllers, the Apex is seemingly one of the best balances between monitoring and control. That being said, the Neptune Apex does miss the mark on Nitrate and Phosphate monitoring. For these, you may consider adding either a Reefbot or Mastertronic. Sadly, these do not interface with the Neptune Apex.

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To monitor these parameters with the Hydros system, there are a number of ways to set this system up. This is great for anyone that wants to really DIY their own equipment. That said, Hydros has a much easier way to solve this coming soon? The new Hydros X10 provides all of the ports needed for temperature, salinity and pH monitoring. Unfortunately, there is also not a hydros solution for calcium, magnesium, nitrate nor phosphate at this time.

While Hydros may not be able to measure some of these parameters, the Hydros controller plays nice with other devices on the market. So, for these parameters, you will need to add on something like the Mastertronic to integrate in with the Hydros. Unfortunately this adds about $1,299 to the total. However, by doing this you get all of the monitoring you would want and get to tie it into a controller!

Hydros Aquarium Controller - Parameters Available

UnitSalinityTemperaturepHAlkalinityCalciumMagnesiumNitratePhosphateCurrent Price
Hydros Controller X4 PackNot AvailableIncludedIncludedRequires MastertronicRequires MastertronicRequires MastertronicRequires MastertronicRequires Mastertronic$659.99

Hydros Aquarium Controller Price

As for pricing, the X10 has not been released yet. So for now, you could use a Hydros Controller X4 Pack to start with temperature and pH for $659.99 and the Mastertronic for $1299. Bringing the total to $1,958.99. This would not get you salinity monitoring, but you would get the addition of Nitrate and Phosphate.

UnitCurrent Price
Hydros Controller X4 PRO Pack + Mastertronic$1959.98

Hydros Aquarium Controller - Final Thoughts

Sadly, this is a really high price point and lacks parameters like salinity. While it's nice that you could control Nitrate and Phosphates, the reality is that these parameters don't typically need "control", but rather monitoring. Control is nice to have, but I'm not convinced the control of nitrate and phosphate out-weighs the benefits of monitoring salinity. Especially when you close in on $2000...

On a side note, there is an X10 that will be released "soon", and this will contain salinity. However the price may determine if it is realistic or not.

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GHL ProfiLux

The GHL Solution includes the ProfiLux 4 Mega Set, which can handle temperature, salinity, pH, as well as ORP. For alkalinity, you will also need the GHL KH Director. While GHL also had the Ion Director for calcium, magnesium, and nitrate, this product has not been available for quite some time due to supply chain issues. Meaning there is not currently a solution for these parameters.

GHL ProfiLux Aquarium Controller - Parameters Available

UnitSalinityTemperaturepHAlkalinityCalciumMagnesiumNitratePhosphateCurrent Price
GHL ProfiLux 4 (Mega Set)IncludedIncludedIncludedRequires KH DirectorRequires Ion DirectorRequires Ion DirectorRequires Ion DirectorNot Available$949.90
GHL ProfiLux 4e (Starter Set)Not AvailableIncludedIncludedRequires KH DirectorRequires Ion DirectorRequires Ion DirectorRequires Ion DirectorNot Available$739.90
ProfiLux Mini Wi-Fi-SetNot AvailableIncludedIncludedRequires KH DirectorRequires Ion DirectorRequires Ion DirectorRequires Ion DirectorNot Available$399.90

GHL ProfiLux Aquarium Controller Price

The initial set of controller/probes is only $949.90, however, to add on alkalinity with the KH Director is another $719.92, bringing the GHL setup to $1909.80. Sadly, this includes less options than the competitors so it seems a bit over-priced and under-performing. While they do have additional, lower cost options available, you will lose the ability to measure salinity. Even at that, the cheapest option comes in just over $1,100 and would only support pH, Temperature, and Alkalinity. The other parameters require the Ion Director for an additional $967.90. And that is only if they actually come back on the market...

UnitCurrent Price
GHL ProfiLux 4 (Mega Set)$949.90
GHL ProfiLux 4e (Starter Set)$739.90
ProfiLux Mini Wi-Fi-Set$399.90
GHL KH Director$719.92
GHL Ion Director$967.90

GHL Profilux - Final Thoughts

I'll be a bit direct on this one... GHL highly over-valued their controller line. It requires a lot of additional components, such as a dosing unit for each "director". Additionally there is no real "WOW" factors about their controller. It comes in as one of the most expensive options and they still haven't solved their supply chain issues as of the time of writing this. I just don't have a lot of great things to say here...

Reef Stable Rating:


Supplemental Reef Chemistry Testers / Monitors

I wanted to add to this article the non-controller reef monitoring options. Some of these can integrate with other reef tank controllers, or act as stand-alone monitors for parameters that the reef tank controller doesn't monitor. For example, if nitrate and phosphate are important to you, then you will likely need to supplement the controller with one of these monitors.

Focustronic Mastertronic

Focustronic has released a monitoring solution for some of the harder to test parameters in your reef tank! The Mastertronic provides testing for alkalinity, calcium, magnesium, nitrate, and phosphate! In fact, it can also be used for ammonia, iodine, iron, OLI, or nitrite. With all of this complex testing, the irony is that it cannot test the simpler, more important parameters such as temperature, salinity, or pH. You will have to combine the Mastertronic with the probes from another controller, such as the Apex or Hydros, to get the added monitoring and control with the mastertronic handling the more difficult testing.

In terms of pricing, the Mastertronic is $1299.99. However, you will need to add a controller for the probes which is as expensive as you choose. The Hydros options tend to be cheaper for this monitoring though.

Focustronic Mastertronic - Parameters Available

UnitSalinityTemperaturepHAlkalinityCalciumMagnesiumNitratePhosphateCurrent Price
MastertronicNot AvailableNot AvailableNot AvailableIncludedIncludedIncludedIncludedIncluded$1299.99

Focustronic Mastertronic - Final Thoughts

Unfortunately the Mastertronic is not really a controller, but more of a tester. I say unfortunately because if it was a controller with the additional probes to really lock down your tank, this is a REALLY GOOD option. Thankfully, the Hydros aquarium controller does integrate the Mastertronic. So the combination of these two could be well worth the money if you are looking for a FULL CONTROL solution.

The one thing I would really like to see is the addition of pH, salinity, and temperature because these are important if you want to see the full picture of what's going on in your reef. Not to mention, they help correct minor incorrect values for most tests.

Reef Stable Rating (Monitor Only):


Reef Kinetics Reefbot

The Reefbot Lab is much like the Mastertronic. It conducts titration tests using other test kits' reagent. The reefbot can test pH (test kit, not probe), Alkalinity, Calcium, Magnesium, Nitrate, Phosphate, and even Nitrite, Ammonia, Copper, and Iodine. Again, like the Mastertronic, you will need a separate controller to monitor temperature and salinity.

Reefbot Lab - Parameters Available

UnitSalinityTemperaturepHAlkalinityCalciumMagnesiumNitratePhosphateCurrent Price
ReefbotNot AvailableNot AvailableIncludedIncludedIncludedIncludedIncludedIncluded$1299.00

Reef Kinetics Reefbot - Final Thoughts

The Reefbot Lab goes for $1299, lining it up with the Mastertronic. Unfortunately, contacting Reef Kinetics seems very difficult. I tried to contact them multiple times about the Reefbot V2, since it is a lower cost option that has been out of stock for over a year, and can't get anyone to reply. Additionally the device seems like it is quite hobby-grade. Less manufactured than alternatives like the Mastertronic.

Combining the high price point and lack of contact, honestly, I would probably pass on the Reefbot until they get things back in-line with their service and go with the Mastertronic.

Reef Stable Rating (Monitor Only):


Which Controller Would I Choose?

I'll admit, this is tough because it depends on what you want to monitor. If you only plan to monitor and control pH, temperature, salinity, alkalinity, calcium, and magnesium (the main parameters), I would get the Neptune Apex with the Trident. It's cost effective, has great support, and is a popular solution in the reefing hobby.

If you want to monitor Nitrate and Phosphate, regardless of the controller, you will need to add a Mastertronic. The real difficult part, is that if you want everything in one place, you will need to use the Hydros controller as it is the only option that can integrate the Mastertronic as an input.

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Often we overthink reef tank control. We see all of the different options and dosing and crazy advanced extra things we can monitor and control. Most of that is extra though. Start with monitoring temperature, salinity, ph, and alkalinity, adding calcium, magnesium, nitrate and phosphate if you'd like. After monitoring these parameters, then add control as you're able. Finally, there are other, cool options that you can add later like leak detection sensors, optical sensors, lights and switches can come when you're ready and are not worth nearly as much as monitoring the parameters.

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About the Author

Reef Stable Founder John Krenzer

John is a Software Engineer with a passion for saltwater aquariums, as well as the founder and president of Reef Stable. He started in the aquarium hobby as a child with a 20 gallon freshwater aquarium. His interest in aquarium life grew and in 2008, John set up his first saltwater aquarium.

Today, John maintains an over 300 gallon reef tank system, consisting of a 120g reef and a 210g reef. These large tanks are contained within the same system, sharing a sump as a means to reduce total maintenance and increase total water volume.

John writes articles for the blog as a means to learn about more reef aquarium topics. These articles act as a reference for the readers as well as himself. John updates these articles frequently to provide additional information or make corrections as new information becomes available.

If you would like to request an article, tank tour article, or to collaborate, let me know via the Contact Me Page!

About Reef Stable

Reef Stable was initially founded in 2019 as a reef tank parameter log to fill a need. Reef Stable quickly grew, becoming a location to solve all of your reef tank problems as well as a place to learn.

Reef Stable now provides a Reef Blog, Reef Aquarium Guides, Coral Care Guides, Identification and Solutions for Pests and Algae, and Reef Dosing Calculators, in addition to the original Reef Parameter Log.

Reef Stable continues to grow, striving to provide a single location for all your reef tank needs!

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