Best 20 Gallon Aquarium Heaters in 2025

★100W aquarium heater is suitable for 10 to 20 gallons aquariums,Length - 9",voltage 110-120V, power cord is 6ft, please choose the right wattage aquarium heater according to our size chart.

★It shows an area to adjust the temperature. It's not exactly accurate but it turns easy and can be adjusted at small intervals

★Explosion Proof: 2mm thickened quartz glass,can be used in fresh water and salt water aquariums,easy to hide in the tank.

All Tetra HT heaters have indicator lights to let you know when the heater is on. It will be red when heating and green when the proper temperature has been reached.

The HT20 uses a built in electronic theromstat to automatically maintain water at 78° F which is ideal for most tropical fish. No adjustment is requried.

Ideal for aquariums between 10 to 30 gallons with hoods or glass canopies

Aquarium heater that blends into the aquarium environment with built-in reflective technology that mirrors the surrounding colors

Computer-calibrated thermostat and easy-to-adjust temperature control dial

Shock resistant Borosilicate glass and high density ceramic heat sick

Superior Safety and Enriched Ambiance: The fish tank heater is constructed with high-quality shatterproof glass and BPA-free plastic, ensuring a safe habitat for your fish. Aquarium heater 50W, power cord 4.75ft, designed for most fish tanks, recommended for aquariums up to 100 Gallons.

Precision in Temperature Control: This aquarium heater excels in providing a customizable temperature range of 68°F-93°F, catering to various aquatic species. Suitable for freshwater and saltwater tanks, it creates a natural environment for your finned friends.

Compact, Versatile, and Efficient: Whether you have a small aquarium heater 5-gallon tank or an aquarium heater 55-gallon setup, this compact heater can be placed horizontally or vertically. Position near a filter or pump for even heat distribution.

Explosion Proof: The aquarium heater is made of 2mm thickened quartz glass, 33% thicker than ordinary glass, explosion-proof, not easy to crack, which is very safe for people and aquatic animals.

Application: 300W water heater is suitable for 35–70 gallon tank, also suitable for both saltwater and freshwater, suitable for fish tanks and turtle tanks, must be completely submerged in water when using.

Accurate Temperature: The fish tank heater can be adjusted from 68°F to 93°F (20°C - 34°C), comes with a thermometer sticker, convenient to detect the water temperature without another pay.

🐟 100W aquarium heater, length 8.8-inch, power cord 4.9ft, designed for small fish tanks, recommended for aquariums 15 to 30 Gallons.

🐟 Adjustable and easy to use: This aquarium heater, adjustable temperature range 68 ~ 93 °F, after setting the temp you want, will on or shut off automatically when the water temperature changes, no extra adjustment is required.

🐟 Accurate Temperature Control: This fish tank heater built-in thermostat, will automatically keep the water at the set temperature within±2°F error. Comes with an sticker thermometer to detect water temp at any time.

🔥【Explosion-proof Quartz Glass Aquarium Heater Durable and Safer】The heater made of explosion-proof quartz glass material and a high-temperature resistant nickel-chromium heating wire with silicon carbide heat conduction,faster water heating and long lasting.2 hours heating 1℃.The shell is a high temperature resistant PC material, which can effectively protect the fish from scalding.

🔥【Temperatures Ranges 68℉ to 93℉,Automatic Heating】The heating rod built-in thermometer,When the water temperature is lower than the set temperature by 1℉, the heater will automatically heat up, and stop heating when the water temperature is consistent with the set temperature.Fahrenheit and Celsius can be converted to each other,Pressing and Press and hold "+" and "-" at the same time, Fahrenheit and Celsius will be converted into each other after 5 seconds.

🔥【LED External Controller with Indicator Light】The controller is not waterproof, please keep away from water，LED digital display screen shows the current water temperature and preset temperature.The number the left on the controller is the current water temperature, and the number on the right is the set temperature,torch light and surrounding lights flicker means heating,torch light and surrounding lights not flicker indicate constant temperature.

Adjustable heat setting 68 to 88°F, Electronic Thermostat accurate to +/- 1°

Shatterproof and nearly indestructible

Fully submersible; Auto Shut-Off when over-heats, resets when it cools down

【Aquarium Heater 200W】-- The 200W aquarium heater produces stable power with quick heat up. It's length is 8.3'', voltage 110-120V, power cord is 5.9ft (cable wire: 4.6ft, power wire: 1.3ft) . Aquarium heater for 20 to 40 gallons, ideal uses for the marine saltwater and freshwater, fish tanks, turtle tanks, betta tanks, small ponds, and so much more.

【Safe and Durable Fish Tank Heater】--The components of this 200W fish tank heater are designed for safety and durability, and encased in a high-durability ABS shell. The nickel-chromium heating wire and quartz glass are made of high-temperature resistant materials, along with explosion-proof quartz sand, giving the product a high level of safety and durability.

【Comprehensive Protection Submersible Aquarium Heater】 -- Our submersible aquarium heater have 2 intelligent protector to avoid damage to the product and its circuitry. ①Over max temp warning, when the temperature is higher than the maximum temperature 94℉/34℃, the code HH appears and automatically stop heating. ②Off-water warning, when the submersible aquarium heater is higher than the level of the fish tank water code E1 appears and automatically stop heating.

Detect Temp Timely: With a built-in thermostat, it will automatically keep the water at the set temperature. The extra thermometer sticker allows you to detect water temp at any time.

Adjustable: Controllable temperature range from 68 °F to 93 °F (20-34 °C). Simply rotate the knob to freely regulate the temperature with deviations from ± 2 °F to ± 4 °F.

Heating Protection: Its indicator light turns red during working and automatically shuts off to stop heating when reaching the set temperature. No danger of overheating to your aquatics.

This 100 watt heater is for aquariums up to 29 gallons. Adjustable temperature dial allows you to set the temperature 1 degree with every click.

Thermal Switch automatically turns off as temperature rises above an internal preset and turns back on once it cools down.

The advanced heating element contains a mica core surrounded by a mesh heating element for superior heat transfer with enhanced durability

FULLY SUBMERSIBLE AQUARIUM HEATER: The 100W Cascade Aquarium Heater easily maintains healthy water temperature within a 1° accuracy, and can be set anywhere between 68 ℉ and 89 ℉, by using the red control knob. The 100W model works great for 15 – 20 gallon fish tanks.

VISIBLE & ACCURATE TEMPERATURE SCALE: With an easy to read setting scale in both Celsius and Fahrenheit, it’s easy to see the temperature adjustments being made. To increase the temperature, rotate the control knob counter-clockwise, and to decrease, rotate it clockwise; or, follow the + and – symbols located near the control knob.

ORANGE PILOT LIGHT: Our Cascade Heat Aquarium Heaters feature a pilot light that indicates the heating cycle status. This means that it will go on and off by itself as the thermostat cycles the heating element on and off. In other words, orange light = heater is on. Similarly, these aquarium heaters make a faint click when turning off.

🐟RAPID HEATING: Faster warming by seconds, the heater material is explosion-proof quartz glass, and nickel-chromium heating wire materials has higher thermal energy efficiency, and then conducts heat through silicon carbide material, is safer and more durable to use. High temperature resistant plastic cover, not easy to deform, and has very strong corrosion resistance.

🐟FREQUENCY ENERGY-SAVING: Auto reduces power when approaching the set tempe, by heated at 10% to 30% power, fully utilizes thermal energy inertia to smoothly reach the set tempe, saving energy. The external controller is easy to operation, every press changes the set tempe by 1℉, ranges from 59℉(15℃) to a max of 93℉(34℃) in order to meet your needs.

🐟INTELLIGENT THERMOSTAT: Over-temperature protection prevents "cooking fish". When the water temp exceeds about 95 °F, flashing 95 number code, red and green light flash together; and over 93℉, the heater will stop heating automatically. When the water temp cool down to below 93℉, the heater will start working auto.

Preset temperature has been set to 77°F, appropriate for most tropical fish, shrimp and aquatic plants requiring stable conditions

With accuracy of ±2°F and overheat protection, protect your tank from extreme temperature

LED indicator light will turn to red when the heater is actively heating

【For Fish Tank 15-40 gallon】200W aquarium heater, voltage AC 110-120V, power cord is 5.0ft, please choose the right wattage aquarium heater according to our size chart. Comes with detachable shield and 2 suction cups. It's easy to hide it in the tank (acrylic or glass).

TEMP ADJUSTABLE: Temperature can be adjusted between 68-94℉. You can set the temp to one of these values on the dial: 68, 71, 75, 78, 82, 86, 90, 94 by rotating the pointer, which allows for complete control of aquatic climate within a 2-degree difference.

SAFETY PROTECTION: Effectively maintain the tank water in the constant temp you set, stop heating when the water temp is 1.5-2℉ above the set temp and restart heating when the water temp is 1.5-2℉ below the set temp.

Fully submersible, auto shut-off when overheats, resets when cools down

Electronic thermostat stops heating once set temperature is reached

Precise temperature setting adjustable to 1° F (68-88° F)

🐠【Rapid Heating and Two Temperature Control System】300W aquarium heater is sutable for 40-70 gallon fish tank and made of the most stable nickel-chromium heating wire, which can quickly and stably conduct heat to the surroundings. It has a built-in temperature control system of Fahrenheit and Celsius(Temp range: 68-94℉/20-34℃). You can press and hold the button next to the controller to switch.

🐠【Intelligent Water Sensor and Automatic Power Off】This fish tank heater has a unique intelligent temperature and water sensor system, the heater will automatically stop/restart heating when the heater is completely out of /in water. and will stop when it rapidly heats beyond the set temperature.

🐠【Explosion-proof Titanium Alloy Tube Aquarium Heater】The submersible aquarium heater is made of explosion-proof Titanium Alloy material and a high-temperature resistant nickel-chromium heating wire with silicon carbide heat conduction, faster water heating and longer lasting.

🐠【New Upgrade】- The 500 watt fish tank heater is suitable for 80-130 gallon fish tank. Double tubes heating element, made of two silicon carbide heating tubes and quality plastic cover for fast, steady, more evenly distributing heat.. IP68 waterproof, explosion-proof and anti-corrosion make it stronger than normal glass and metal heater. Your Fish will be no longer afraid of winter.

🐠【Safety Guarantee】- With anti-dry heating protection and overheating protection, when the water temperature exceeds 93℉, the adjustable aquarium heater will stop heating and alert. It will also stop when the water level is 5cm lower than the heater and the display will display "E1". Escorting your pet's safety all time.

🐠【Smart Temperature Control】- Accurate temperature controls within 1°F difference. The heater will stop heating when the temperature reach the setting and restart when lower than setting. If power is shut off,the memory function will keep the temperature settings until it powers on again. Always provide the best living environment for our cute fish.

Fish Tank Heater: 300W aquarium heater suit for 55 - 80 Gallon fish tank. Voltage:110V, power cord is 5.57ft, Max deep water immersion 20 inch/1.7 FT

Correct installation: Stick the heater vertical onto the tank side near the water intake or on the way of water flow.（This way the heater can quickly sense the water temperature and make adjustments automatically）, Keep the aquarium heater fully submerged in water

Fully Automatic Control: Design with External Temperature Controller, Temperature Range is 68 ºF-90 ºF, when water temperature achieve the setting temperature, heater will automatically stop heating, when water temperature is lower than the setting temperature, heater will automatically start heating

🐠🐠【Excellent function Effect】 300-watt aquarium heaters fit for 50-60 gallon large fish tank, keep your big fish tank warm and comfy. double sensing probe on the top make sure its accuracy when detecting the temperature and water volume.

🎁🎁【Perfect Partner-Strong material advantages】The INKBIRDPLUS heater is made of titanium tube material, which has the performance of anti-breaking, anti-explosion, anti-cracking, and anti-corrosion. This heating rod can be applied to salt water and fresh water, and the heating effect is better than other materials.

🍭🍭【External Controller】The controller with the touch button can adjust the temperature at any time and easily understand the water tank's temperature through the LCD. It is easy to operate from 68℉/20°C to 94℉/34°C (please place the controller outside the fish tank).

SUPER MINI SIZE – This aquarium heater is SUPER SHORT in length – might be the shortest heater in the market. It is only a bit more than HALF of the length comparing with the traditional fish heaters! The innovative super short length perfectly solves the headache of the fish keepers on the traditional aquarium heaters! Takes up less space, easy to hide, but in full power! Temperature range is 64-93F.

ACCURATE TEMPERATURE – Thanks to the intelligent inverter technology, with the in-built chips the thermostat keeps the heater at a constant temperature at an accuracy of 1F, much more accurate than the traditional knob-controlled fish heaters. The thermostat shows 2 readings – the current temperature and the set temperature – very easy to operate.

DRY RUN / OVERHEATING PROTECTION – Full consideration of safety. With the multiple protections this fish tank heater will stop working when the water level is lower than the minimum water level (DRY RUN PROTECTION) or when the water temperature exceeds 97F (OVERHEATING PROTECTION). You are free from “cooking fish”!

🐠【50W Compact Fish Heater】110-120V/60HZ square shape design small aquarium heater, fast heating for small fish tank. 50W tank heater is for 3-10gallon, 100W tank heater is for 10-20 gallon. The power cord is 5ft, long enough for use indoors. With 2 strong suction cups at the back side of the betta heater, it's easy to install it on to glass, acrylic or plastic tank

🐠【Shut off When Out of Water】BOEESPAT aquarium heater adopt newest technology, it is a fully submersible aquarium heater for fresh water and saltwater tank, when the top part of betta fish heater is out of water it will be forcibly stopped. After putting it in the water again, the fault disappears and normal operation resumes.It is a safe and reliable water heater tank

🐠【Small Aquarium Heater with External Controller】You can set the temperature outside the fish tank through the external controller, and the fish tank accessories of temperature sensing built in will cyclic heating the tank water automatically .Temp range from 65℉ to 93℉. Every time you set your betta fish heater, just press the button over and over until it reaches to your desired temp, then stop and wait the digit flashing for 3 times, then setting is done

【More Power and Longer Life】This heater is for 5-10 gallon fish tank, comparing to 25W, this 30W aquarium heater is more powerful and heating the same water in shorten time. Less working time provide longer life.

【Double Safety Protection】2mm thickened explosion-proof glass, 33% thicker than normal 1.5mm aquarium heaters, adding a specialized protective cover wrapping the heater tube, more durable and much safer for both human and aquatic creature.

【Application】30W suitable for 5-10Gallon fish tank, suitable for both fresh and marine water, suitable for all kinds of fish, turtle and plants. Size: 7.5in(19cm) in Length.

✅Upgraded Heater - Our aquarium heater is made of high quality real quartz glass material, will not explode during working, can totally keep your fish safe and health, suit for freshwater and saltwater tank.

✅Circulating Working Mode - Our submersible aquarium heater has a super good feature is after setting your temperature, it will work about 5-10 minutes, then stop 2 minutes, then continue to working, repeat this working mode until get your temperature. This working mode avoid overheating your fish.

✅Adjustable Temperature – The temperature of the water heater can be adjusted, rotate the orange dial can easily set the accurate temperature which you want. Temperature range is 20-34 ℃(68-93 ℉).

This 50W aquarium heater is fitted with stainless steel tube inside and engineering plastic tube outside to protect against damage. No glass components. Equipped with dry-fire protection device.

Temperature range of this tank heater is from 68℉-88℉, adjustable via a simple knob on the top. +/- 1 ℉accuracy. The light will go on while it’s working and off while not.

Can be placed vertically or horizontally. BUT NOT TILTED. It will not operate if the bottom is higher than the top. Must be FULLY submerged.

🔥【25W Small Submersible Heater】Suitable for 1-5 gallon fish tank,Temperature Control Range 59℉-93℉,When the temperature is lower than the set value 1℉, the heater will automatically heat up, and it will automatically stop heating when the set temperature is reached.

🔥【External Controller and Built-in Thermometer】Fish tank heater with a built-in thermometer,display water temperature of the fish tank in real time,HD LED display,The red light when heating, red light off when the temperature is constant, and display error code when the heater fault.The controller is not waterproof, please do not put it into water.

🔥【Easy To Use】Set temperature by press the button until reach your desired temperature value.The display will flash the desired temperature value three times, then return displaying the current water temperature.Your setting is done.You can press the button persistently to display 59-93℉ in a cycle.

Water shortage protection - Built with overheat and water shortage protection. The heater power will cut off when washing tank, changing water and maintaining aquarium, otherwise heating cannot be processed. CF certification

Installation - 300W submersible heater is suitable for 35 to 80 gallons aquariums; Vertical or horizontal installation and ensure the device is fully submerged underwater. With these 3 suction cups, the heater will stick tightly to the surface of tank

Temperature Scale - Compact underwater analog tank heater can be adjusted between 68°F~94°F (20°C~34.5°C). 500 watt fish tank heater holds your 50-90 gallon tank at a constant temperature and recovers quickly after a water change. Note: Due to some unpredictable external factors, it's normal that the temperature difference is ±5°F

𝟮𝟱𝙒 𝘽𝙚𝙩𝙩𝙖 𝙏𝙖𝙣𝙠 𝙃𝙚𝙖𝙩𝙚𝙧: Length - is 6.8 inches, 110V/60Hz, Cord length is 4.0ft, Suitable for 1-5 gallons aquarium, IP 68 waterproof, anti-corrosion, please choose the right wattage aquarium heater according to our size chart

𝙏𝙚𝙢𝙥𝙚𝙧𝙖𝙩𝙪𝙧𝙚 𝙍𝙖𝙣𝙜𝙚 𝟲𝟯-𝟵𝟱℉: Adjustable aquarium heater for easy use, just turn the top knob to freely adjust the temperature you need. We also provide a free sticker thermometer for each customer, so you can observe the water temperature of the fish tank at any time

𝙃𝙤𝙬 𝙞𝙩 𝙒𝙤𝙧𝙠𝙨: Plug in the power supply and check whether the indicator is on. The yellow light means the heater is working. When the water temperature is lower than the set value, the fish heater will automatically start heating. When the water temperature reaches the set value, the heating will stop and the indicator lights off

[Real Smart And Fast Heating]. A good partner for your beloved fishes! SZELAM aquarium heater adopts black quartz sand to conduct heat, which features a high-speed and all-round heat transfer effect that can quickly increase the water temperature. It stops heating when the water temperature is close to the set temperature and continues when the water temperature is lower than the set temperature.

[Upgraded Protective Cover]. The fish tank heater 100w will be a livesaver to your aquatic pets. It will never scald your little fish, as the protective shell is designed with dense small holes, which can protect your fish from being scalded, as well as dissipating the heat to the whole tank.

[Precise Dual Temperature Control]. Both suitable for freshwater and marine water,this aquarium heater 100watt is explosion-proof & anti-scalding. With built-in sensitive temperature control and intelligent heating function, the fish heater can provide accurate and stable temperature when working, while creating a worry-free habitat for your beloved fish.

Safe Rugged Construction -- Built in shatterproof QUARTZ tube wrapped with two heating element mica plate and nickel wire, along with high-impact plastic housing, hygger submersible Aquarium Heater ensures the safety of your pets while maintaining proper temperature.

At-A-Glance Temperature Display -- heater rod shows real time water temperature and indicator light. It will be red when heating, green light when the proper temperature has been reached.

External Knob Controller Memory Function -- allows you quick set temperature without getting hands wet especially in winter, adjustable wide temperature range of 59°F to 93°F in 1-degree increments. Memories last setting when you unplug it to water change.