How To Avoid Catastrophic Heater Failures in Your Marine Aquarium - Preventing Disaster

Welcome to Simple Reefs. We are a brand new website designed to take the stress and expense out of starting your very own marine aquarium. With us being a brand new website, we have been looking at some of the basics of Marine Aquarium ownership. One of the big topics that we have been looking at, as of late, is aquarium heaters. Today, we are talking about something incredibly important. How To Avoid Catastrophic Heater Failures in Your Marine Aquarium.

The Potential for Disaster

We’ve talked a lot about how important maintaining thermal stability is to your marine aquarium. To quickly recap, the coral, fish, and invertebrates in your tank come from tropical climates where there is very little variation in how warm the sea is. This means they are ill equipped to handle fluctuations of temperature.

So much so, in fact, that they can suffer from something known as thermal shock when temperatures change too much in either direction. This can cause lethargy, heavy breathing, and even death in fish and the bleaching of coral as their symbiotic algae abandons them.

While gradual increases in the water temperature of your tank may not be a complete disaster. Affording you the opportunity to correct the problem and reverse the damage caused. What happens when you have no such chance to fix the issue? What happens when the temperature change is both sudden and drastic?

When Aquarium Heaters Fail, Disaster Follows

There is one glaring reason why you may experience a sudden and rapid increase in temperature in your aquarium. External factors are unlikely to cause this to happen. Even a heatwave will only result in fairly minor fluctuations. The primary cause of a rapid increase in water temperature is likely down to a failed aquarium heater.

The troubling truth of the matter is that when a marine aquarium heater fails, it does so in one of a few ways.

• The heater coil fails so the water won’t heat.
• The power source fails so there won’t be power to the heater rendering it useless.
• The structural walls of the heater fail causing it to explode (mainly old fashioned glass heaters).
• The thermostat fails so the water will heat continuously.

I have experienced all but one of these problems with aquarium heaters over my fishkeeping life. Luckily, the third issue on the list, an exploding heater, only happened in water mixing buckets as I never use glass heaters in aquariums. The first and second were minor inconveniences because, again, they were heaters used for mixing water.

If the heater suddenly stops doing its job and won’t heat the water anymore, your temperature will drop. Most ambiently warm homes won’t notice a huge problem, here. The tank’s temperature will hover around the 20 degrees Celsius mark and your fish might look a bit listless but you will likely avoid a major aquarium crash.

The final item on that list is the one that should inspire fear into the hearts of anyone who owns a marine aquarium. The reason for that is because when a thermostat fails on a heater, unless that heater features “Overheat Protection”, it is going to stay on and carry on heating up the water.

A Failed Heater Thermostat Can Mean Catastrophe

When the thermostat fails on an aquarium heater that doesn’t feature overheat protection it will be unable to switch itself off. This is due to the way thermostats in aquarium heaters work.

We talked about it in our article on The Importance of Marine Aquarium Heaters. The thermostat is the brains of the heater. It measures the temperature of the water and decides when to switch the heater on.

When the water gets too cool, it turns the heater on. When the water reaches the designated temperature, it turns it off. The problem is, when a thermostat on a marine aquarium heater fails, they tend to get stuck in the “On” position.

This means the heater coil that does the important job of warming the water will stay activated. Naturally, the result of this heater coil being activated is that the heater will continuously heat the water around it, completely unaware of whether it is too hot or not.

This can be absolutely catastrophic. Remember when we talked about the size of heater you need for your aquarium and how 1 litre of water, generally, requires 1 watt of heating power? If you own a single heater that is rated for the entire water volume of your tank and that heater fails, you are in serious trouble. Let’s explain why.

Your Heater Isn’t Continuously Heating Your Water

When you use an aquarium heater in your marine tank, it isn’t constantly heating the water. It is only switching on and heating the water for very brief periods of time. In fact, most aquarium heaters will only be actively heating the water for around 12 hours a day, perhaps even significantly less in warm homes and climates.

If the heater were to remain active the entire time and carry on heating the water, the water temperature would climb quickly. That’s why the thermostat is so important, particularly when you have one single heater powerful enough to heat your entire tank. It’s going to prevent that from happening and only heat the water when it needs to.

When that thermostat fails, that heater will be unable to turn off and, due to its ability to heat your entire tank on its own, it is going to carry on heating the water relentlessly. It, literally, won’t stop increasing the temperature until the water has reached the maximum temperature that the heater is capable of producing. This could be many degrees higher than what your fish, invertebrates, and coral can tolerate.

Potential Tank Annihilation

It is not hyperbole to suggest that a heater with a stuck thermostat can wipe out your entire tank. Just take a look at this post on the highly regarded forum Reef2Reef. Many owners have experienced multiple heater failures and each has the potential to completely wipe out everything in your tank other than the hardiest of fish (usually clownfish).

As we talked about earlier, your fish and coral come from tropical climates and experience very little in the way of temperature fluctuations. They simply aren’t adapted to drastic increases in temperature and will very quickly succumb to high temperatures. That’s without mentioning the decrease in dissolved oxygen in warmer water that can lead to them suffocating.

A heater with a stuck thermostat is a catastrophe, there is no other way to put it. There are few things in marine aquarium ownership that are so potentially deadly. Without some careful planning, everyone is at risk of this happening.

How To Avoid Catastrophic Heater Failure

The good news is, there are ways to avoid the worst case scenario. There are steps we can take to prevent the issue ever occurring, to help recognise the problem when it does occur, and to minimise the damage should the worst happen. Let’s take a look.

You Absolutely Need a Thermometer: This is something that is very overlooked in the marine aquarium hobby. You absolutely need to have a thermometer measuring your tank’s water temperature that is visible at all times. This won’t prevent catastrophe but it will inform you of when the worst case scenario is taking place.

Cheap digital thermometers have a highly visible display, take cheap batteries, and have a probe which can sit in the water to measure temperature. Some even have alarms that you can set to sound when the temperature reaches a certain point. More expensive thermometers even offer smart features to alert you on your phone, via an app, or even using smart assistants like Alexa.

Checking your thermometer multiple times a day will allow you to have a heads up as soon as something goes wrong. It is an essential item and should be included in any marine aquarium owner’s tool chest. Having two, each at opposite ends of the tank, is even better.

Use Two Heaters Rather Than One: Remember when we talked about the size of heater you need for your marine aquarium? We mentioned how, in typical cases, 1 litre of water will require 1 watt of heater power. You can check for yourself on our handy Heater Size Calculator. Well, whatever that required wattage heater is, divide the number into two smaller heaters rather than one.

For example, for my 400 litre tank, I need an approximately 400 watt heater. Rather than buy one single heater capable of warming my tank, I buy two 200 watt heaters. This is going to give us a couple of huge benefits.

Placing two heaters on opposite ends of the tank will guarantee a more even heat distribution which should be more efficient; if one of our heaters stops working and won’t heat the water anymore, we will still have one active heater to keep the water warm; and, should the worst happen and our thermostat gets stuck in the on position, the heater will be too underpowered to cause any real damage.

That’s three huge benefits:

• More efficiency and more even heating
• Redundancy if one heater fails
• Smaller heaters are too underpowered to do any real damage should the worst happen.

This may be all you need to avoid the worst case scenario so, wherever possible, purchase two smaller heaters rather than one single, optimally sized, heater. Particularly when it comes to larger tanks that require more power to heat.

Avoid Cheap Aquarium Heaters: Cheap aquarium heaters are far more prone to failure than high quality heaters. We talk all about it in our article on which type of heater should you buy. I would go as far as to say that a cheap glass aquarium heater will definitely, without question, fail at some point. The only question is when. Whether that is a simple power supply issue, a catastrophic explosion, or a thermostat failure is simply down to luck.

Try to purchase heaters from well known brands that have a lot of positive reviews. Avoid glass heaters wherever possible. The best, and safest, combination is a titanium heater with an external controller. Titanium heaters are far more robust and don’t typically have a thermostat which is why they have to be used with an external controller. It is one less point of failure.

Use an External Controller: An external heater controller is the ultimate failsafe should anything go wrong. An external controller provides a degree of separation between the heater and the heater’s own thermostat. Rather than relying on the thermostat that comes with the heater itself, an external controller will measure the water’s temperature independently and then turn the heater on when it is needed.

An external controller will usually feature a display, a temperature probe, and a plug socket. They are, really, quite simple to use.

• You take your heater and position it in your tank or sump
• You plug the heater into the plug socket on the external controller
• You place the thermometer probe from the controller into the water away from your heater
• You set the desired temperature on your external controller.

The controller will detect the temperature of your tank’s water using the temperature probe. When it notices a drop of a certain, pre-set amount (usually a degree or two), it will activate the power to your heater, turning the heater on. When the probe detects that the temperature is back to normal, the controller will turn your heater off.

Using an external heater controller will mean that, even if the worst happens and your heater’s thermostat breaks, the heater will still be switched off when the desired temperature is reached. Most external controllers will sound alarms when temperatures get to certain set points, as well.

It can seem like an extra unneeded piece of equipment but external heater controllers are actually extremely affordable and provide a huge amount of additional security should the worst happen. Just always be sure to place the controller’s probe securely in the tank and make cleaning the probe part of your regular maintenance.

You need to be sure that the probe won’t come out of the water as that can cause a lot of problems in itself. The controller will believe the tank’s water is the same temperature as the ambient air in your room. This will cause the external controller to turn the heater on in an attempt to warm the tank up. Due to the fact that the probe will be measuring the air temperature and not the water temperature, the heater will stay on as the temperature will never increase.

Nothing is Completely Fool-Proof

Unfortunately, none of these tips are completely fool-proof and guaranteed to avoid catastrophe. The best we can suggest is to use a combination of these tips to achieve as close to complete safety as possible. In the ideal scenario, you would use two good quality, not glass, underpowered heaters rather than one, preferably with overheat protection, an external controller to manage them, and two thermometers at either end of your display tank.

This way, you aren’t relying on the heater’s own thermostats. Your external controller can disable the heaters should the worst happen. A failed thermostat won’t overheat your tank because the heaters are physically incapable of warming the water enough, alone. And you will have a visual reference point that you can check multiple times a day so that you have a heads up in case of an issue.

Obviously, you will want to be maintaining your heaters, as well, to help keep them working optimally. We are going to be talking all about that in an upcoming article. For now, thanks for reading and spending your time at Simple Reefs.