Since most of the fish we keep come from tropical environments, water temperatures must be maintained somewhere between 72 - 78° F at all times.  For those of us that live outside of tropical latitudes, an aquarium heater is absolutely mandatory for maintaining those constant water temperatures. Heaters are under constant use and critical to the lives of the aquatic animals in our care.

For this same reason, heaters are also the #1 piece of aquarium equipment to unexpectedly fail and lead to a life-threatening situation. The wear and tear on your heater is unavoidable and fluctuating temperatures are deadly. Good news is we have some best practices that can help you avoid a heater-related disaster and be prepared for when the inevitable failure occurs.

Types Of Aquarium Heaters

A heater is essentially a probe that is submersed into the aquarium water. The probe heats up, warming the water around it, and will automatically turn on/off based on a thermometer and control device. For effectiveness' sake, it is important to recirculate your aquarium water at all times around that heater. 

All aquarium heaters are very similar in both form and function with just a few key differences. Glass and titanium are the two most common types of heaters and the recent addition of plastic heaters is a welcome addition to the lineup.

  • Titanium Heaters - Small form factor, durable, and require a separate temperature controller.
  • Glass Heaters - Large form factor, breakable, but usually have an integrated thermostat.
  • Plastic Heaters - Small form factor, durable, and have an integrated thermostat.

How An Aquarium Heater Works

Most glass and plastic aquarium heaters have an integrated thermostat that turns the heating element on/off.  The mechanics behind this can vary slightly from brand to brand but the result is the same, the heating element is automatically turned on/off by monitoring water temperature. The user sets the desired water temperature for the heater to maintain.  

Titanium heaters operate this same way but don't have that control function integrated meaning you will need to plug the "titanium heating element" into a separate temperature controller. The temperature controller has a thermometer to monitor water temperatures and a controllable power switch that plugs into the wall. Temperature controllers are digital and can be programmed by the user to turn on/off as desired and usually has a calibration function where you can calibrate the thermometer readings. You also get some flexibility in the differential or the distance between the on and off temperatures which directly controls how often the heater switches on/off. Sometimes the titanium element and controller are bundled together but sometimes you need to purchase them separately. 


No matter what kind of heater you choose to use, it is always a good idea to have redundancy solutions because ALL aquarium heaters are subject to failure. As an aquarist, you will eventually experience some kind of failure with your heater.  Whether the element gets stuck ON and overheats the water or if it fails to heat the water sufficiently, both situations can be life-threatening.

  1. Temperature Monitoring and Alerts - Always have a separate thermometer to monitor water temperature in the display aquarium in addition to the heaters control device.  At a minimum, use a classic analog thermometer that will give you an indication of water temperatures at a glance. At best, have something that will notify you directly with an audible alarm or better yet, a notification on your phone, when temperatures fall out of range. 
  2. Have a Backup - To prevent temperatures from dropping when the heater stops working, always have a secondary heating solution on hand. You can automate this by installing a secondary aquarium heater with a lower setpoint than your primary. If the primary fails and water temperatures fall to that lower setpoint, the backup heater kicks on and maintains temperatures.
    • Primary heater setpoint: 78° F
    • Secondary heater setpoint: 74° F
    • At a bare minimum, have an extra heater on hand at all times so you can at least remove and replace a broken heater when it happens.
  3. Use a Temperature Controller - This is the best solution for preventing an overheat experience where a heater gets stuck in the ON position.  You want to plug your primary heaters into some sort of "overlord" type temperature controller that will cut power to the heaters in the event they overheat the water. Ideally, you are then notified should that occur. Aquarium Controllers like the Neptune Systems Apex are great for this function but you can also use something like the Aqua Logic Temperature controller.  
    • Primary heater setpoint: 78° F
    • Temperature controller setpoint: 80° F

Benefits of Temperature Controllers

Using a temperature controller has some great benefits, whether it be used to control a titanium element alone or to oversee your glass/plastic heaters.

  • Increases the lifespan of your heating element because you can widen the gap between your on and off temperatures.
  • You get real-time water temperature readings at a glance.
  • They use external temperature probes that can be located in your display for a more accurate water temperature reading.
  • They often have an audible alarm feature and in the case of the InkBird Wifi, they will notify your phone! 

How To Choose an Aquarium Heater

Water Volume: So the first thing you should do is consider the total water volume in your aquarium. More water means you need a stronger heater. 

Ambient Air Temperature: Consider the air temperature around the tank and how hard the heater needs to work in order to maintain the target water temperature. The closer the air temperature around the tank is to your target water temperature, the less the heater needs to work.  For example, an aquarium placed in a room that is maintained at 65° F will require a stronger heater than if the air temperature was kept at 72° F.  If your home is climate controlled, this means your heater won't need to work as hard compared to situations where your home is more subject to seasonal air temperature changes. 

Durability: In this case, just think about where the heater is going to be located and the chances of it being broken.  Titanium and plastic heaters are less likely to be damaged in the event they are bumped, dropped, or crushed while in the tank. 

Redundancy: This is a simple one, choose a heater that has a temperature controller and be sure to always have a backup heating element of some kind. The exact setup can vary but temperature controllers are almost always the best choice compared to relying on an integrated thermostat alone. 

Dimensions: Make sure the heater will fit into your sump or aquarium where you need it to go. This usually means checking the water depth to ensure you can effectively submerge the entire heater as instructed by the manufacturer but also ensure the total length is not too large to get the heater in and out. 

Wattage: Heaters are sized according to wattage which directly refers to their heating power. The general rule is to choose a heater that can supply 3 - 5 watts of total heating power per gallon. For example, a 20-gallon tank should have a 60 - 100 watt aquarium heater.  If air temperatures are cold around the tank and you're dealing with a larger volume of water, choose the higher wattage end of that spectrum and vice versa.