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Automating Reef Tank Temperature Control

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Last updated on November 17th, 2023


Automating Reef Tank Temperature Control

Automated Reef Tank

This article about automating temperature control is part of a series of articles I am writing about how to automate a reef tank. In theory, a fully automated reef tank would require you to do absolutely nothing. In reality, any of us that own an aquarium know that is unlikely at best but essentially not possible. That being said, what if we automated 90% or more of the reef tank? Then you would only need to worry about things like cleaning pumps, saving coral that fell over, and other minor jobs.

While each part of automating a reef tank comes with different layers of cost and difficulty, you will need to decide how far you want to take the control. A perfectly controlled environment is expensive and complicated, but one that hits 80-90% may be far less! It's really up to you to decide how far you want to go and how much you're willing to do yourself.

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Reef Tank Temperature Control Automation

Automating reef tank temperature control is likely the most important parameter to automate, and also one of the easiest. Since temperature monitoring is a fairly simple number, there is very little in terms of complex considerations. That said, there are a couple of ways to have redundancy in case of failure, placement of temperature probes, and even energy saving methods like two-stage heating.

While I'll talk about perfect world automation, take this as far as you'd like. Remember, most people have a heater and sensor in their sump or tank, and that's it. So if you don't do full temperature control automation, it's perfectly okay.

How I assume your tank is set up

There are a lot of different types of reef tanks and ways to set them up. Some of the popular ones include using an overflow with a sump, all-in-one that have a "sump" in the back, and even standard tanks with hang-on-back equipment. Since I honestly don't have the time to talk through each and every option for how to automate reef tanks, I am picking the most common option, an aquarium with an overflow and a sump.

While this is the example, it's fairly simple to use the same setup in your tank. For example, an all-in-one tank will just use the back instead of the sump. A tank with hang-on-back equipment will either be on the back or in the tank. Just because your tank's picture isn't below, doesn't mean it doesn't work the same.

Basic Aquarium Setup

Reef Tank Temperature Automation Goal

The goal of automating reef tank temperature is to maintain a stable temperature as well as the correct temperature in the Reef Tank. While most often the heaters are in the sump, we are not as worried about the sump temperature, but rather the temperature in the reef tank.

Temperature Controllers

Right off the bat, I suggest you have at least one Inkbird Aquarium Temperature Controller. The temperature sensors in the heaters themselves is not very accurate, and typically fails. I don't use them at all. I use the Inkbird Controller and another temperature sensor as a backup in case the Inkbird sensor comes out of the water or fails all together.


Ideally, you will want two Inkbird Aquarium Temperature Controllers. You can split the total amount of heaters needed between the two controllers. Then if one fails, you still have the other keeping your tank heated.

Multi-Stage Aquarium Heating

Another reason for two temperature controllers is to save energy while maintaining more stability. Multi-Stage aquarium heating is when one reef tank temperature controller is set 1 degree lower than the other. This way if the temperature can be brought back to the right number with only one heater, it only uses the one. If the temperature slowly drops that extra 1 degree, then both heaters will be on to bring the aquarium back up to temperature.

If you are going to do multi-stage aquarium heating, you will need to size the heaters correctly. You will want each heater to be roughly 75% of the needed heater. For example, if you need a 500w heater, instead, use two 300-400w heaters instead. If the first one can't keep up, the second heater will kick in to keep temperature in check. If there is a low demand for heat, only one will turn on, leading to lower fluctuations.

Temperature Sensor and Heater Placement

The next piece is where do you put the heater and the temperature sensor to automate reef tank temperature control? The best place to put heaters and temperature sensors is in the aquarium itself. Then heat is directly added to the tank, and the measurement is in the tank itself as well. For some people, this isn't a problem. For most of us, the cords in the tank are an eye-sore and not acceptable!

Reef Tank Temperature Control In Tank

In that case, you can put the heaters and sensors in your sump. If you do this, there are a couple things to remember. The first is that the temperature sensor should be near the water coming into the sump from the tank. This way, the temperature being measured is very close to the temperature in the aquarium.

Next, the heaters need to be in a chamber after the temperature sensors. Otherwise, the heat from the heaters will cause the temperature sensors to measure wrong. I do suggest keeping the heaters in a location where water must come in contact, such as near the baffles.

Reef Tank Temperature Control In Sump

Which Reef Tank Heater Should I Use?

If you don't know what kind of heater to buy, check out my article, Simple Rules for Picking a Fish Tank Heater. If you are running large aquariums, over 500 gallons, you may also be interested in How To Heat an Aquarium with Natural Gas.

Adding a Reef Tank Controller

The next step in reef tank automation is to add a reef tank controller such as an Apex or Hydros. While not needed for temperature control, it does give you the ability to monitor temperature and turn the temperature controllers off if they fail. Additionally, for more advanced automation in reef tanks, you will need a reef tank controller.

Temperature Notifications

One of the main benefits of adding a Reef Tank Controller such as the Neptune Apex or Hydros is to get an alarm on your phone if anything goes wrong! You can set high and low limits so you will get notified if your reef is freezing or overheating.

This let's you know when something is wrong, but even better, let's you fix it quicker! As an added benefit, you can set the alarms not only to a "danger" point, but maybe a little before. That gives you more time to get home and get things under control should your reef be even 1 degree out of line.

Extra Failure Control

Another bonus of the reef tank controller is that they can save your reef in case of a heater failure or even temperature controller failure. If you plug your inkbird into the power control (i.e. EB832) of your reef tank controller, you can put extra safe guards in place.

What I do, is in addition to the notifications, if the temperature gets too high, the controller turns the temperature controllers off. If you have a chiller, you could do this if the tank gets cold as well. This way, if the inkbird fails, or its probe comes out of water, your reef will still be safe!

While this may not be perfect, it adds another layer of safety and security to your reef!

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As far as automating a reef tank, temperature control is one of the simpler parameters to control. With a little redundancy and proper placement of equipment, you can have stable reef tank temperature at a low cost. While not needed, you can even use a reef tank controller such as the Hydros or Apex to monitor temperature and even turn off the temperature controllers if they fail. Adding even more automation to your reef tank.

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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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