Fluval Electronic Aquarium Heater, 300-watt

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$62.43 Chewy Price
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About This Item

Details

  • Intelligent digital microprocessor monitoring system and dual temperature sensors continuously monitor and display the current water temperature.
  • Precision temperature control allows you to set the temperature between 68 and 93 degrees F in 0.5-degree increments.
  • High and low temperature alerts provide constant peace of mind.
  • Integrated fish guard prevents your fish from coming into contact with the heating element.
  • Fully submersible; suitable in fresh and saltwater aquariums up to 100 gallons.

Instructions

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Questions & Answers

11 Customer Questions

Is this heater fully submersible?

Answer by Chewy • Aug 29, 2018
This Heater is fully submersible; suitable in fresh and saltwater aquariums up to 100 gallons.

I have a tank that’s 120 gallons will this heater work?

Answer by Chewy • Feb 27, 2018
This heater is suitable for fresh and saltwater aquariums up to 100 gallons.

Is this to big for my fluval evo 13.5 gallon nano tank? I know the temp will stay where I set it but what I'm asking about is the actual size. I noticed that you had different sizes after I ordered the 300w. Are they all the same dimensions?

Answer by Chewy • Mar 26, 2018
The Heater measures 18.2 x 3.3 x 1.8 inches for the 300 watt, the other Fluval Heaters may be different sizes.

Will this heater shut off if the water gets too hot? I know it indicates when the waters too hot. Just want to make sure it also maintains the temp I set it at.

Answer by Chewy • Apr 12, 2018
During normal operation, when water temperature is within -1/+1 °C or -2/+2 °F of the set temperature, the backlight of the LCD screen is green. If water temperature exceeds the set temperature by 1 °C or 2 °F, the LCD’s backlight will turn red. Ifwatertemperature is lowerthan the set temperature by more than 1 °C or 2 °F, the LCD’s backlight will turn blue. If ever the temperature goes outside -/+3 °C or -/+5,5 °F of the set temperature, the display will provide an alert by flashing.
Reviews
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4.0
Rated 4 out of 5 stars
98 Ratings
Terms & Conditions

74 Customer Reviews

Rated 3 out of 5 stars
By Leah on Nov 28, 2025

200 Gallon Tank Setup - Frequent LF Warning

I have 2 of these heaters in a 200 gallon tank. My tank is 6 feet wide and I have one heater on each side. As other have said, the Low Flow "LF" is a constant issue

I have 2 of these heaters in a 200 gallon tank. My tank is 6 feet wide and I have one heater on each side. As other have said, the Low Flow "LF" is a constant issue and I am not sure how accurate that gage is. Just now the temp showed 77 and in less than 2 minutes it jumped to 82 with a red light indicating LF. It shouldn't be possible to jump 5 degrees like that in 2 minutes. What I think is the actual problem is the casing around the heater preventing proper flow. I position air stones directly below the heaters to keep flow constant and extra air stones to keep water flowing to the sides to help keep heat circulating away from the heater. I get nervous leaving the house with these on. If I move the heater just a bit the LF indicator goes away and the temp display will immediately drop 2-3 degrees, so I really don't know if that temp gage is accurate or buggy.

Rated 5 out of 5 stars
By Al on Jan 13, 2026

Fluval 300W heater

This is the 3rd heater of this size I've bought. You can easily digitally set the temperature and it gives you aquarium temperature. These are worth the purch

This is the 3rd heater of this size I've bought. You can easily digitally set the temperature and it gives you aquarium temperature. These are worth the purchase.

Rated 4 out of 5 stars
By Angela on Dec 7, 2025

Safety first

I love that the heater itself is enclosed to prevent direct contact as my turtles think anything in their tank is a toy. Water always seems to be a couple degrees

I love that the heater itself is enclosed to prevent direct contact as my turtles think anything in their tank is a toy. Water always seems to be a couple degrees less than I set it at but that's easy enough to accommodate.

Rated 5 out of 5 stars
By David on Oct 15, 2025

Works Well

Replaced a dying Aquarium-coop heater as they no longer are available. I like having a digital readout (which I have become accustomed to with the previous heater),

Replaced a dying Aquarium-coop heater as they no longer are available. I like having a digital readout (which I have become accustomed to with the previous heater), so this was the only one I could find that gave me that feature. I have only used it now for about 1 month, but it is working without a problem. I have it in a 55-gal planted tank.

Rated 1 out of 5 stars
By bill on Nov 15, 2025

It doesnt work right

It doesnt keep temp and constantly throws LF fault code.i.e. low flow.not true.tons of "flow" present in tank

It doesnt keep temp and constantly throws LF fault code.i.e. low flow.not true.tons of "flow" present in tank

Rated 5 out of 5 stars
By Diane on Feb 6, 2026

Easy temperature viewing

Warmed the tank nicely. Turtle is eating again.

Warmed the tank nicely. Turtle is eating again.

Rated 1 out of 5 stars
By Amanda on Sep 1, 2025

The bulb in it was shattered

We noticed that it never started heating the water so when we took it out we noticed the bulb in it was completely shattered. Really hoping nothing from the shattered

We noticed that it never started heating the water so when we took it out we noticed the bulb in it was completely shattered. Really hoping nothing from the shattered bulb leaked into my tank.

Rated 3 out of 5 stars
By Mo in Montana on May 21, 2025
Received Free Product

Maybe better in a bigger tank

Tried it in my 29 gallon tank, maybe too big for the tank? Wasn't happy that there was a 2 degree difference between it and the other digital temp readers. Had

Tried it in my 29 gallon tank, maybe too big for the tank? Wasn't happy that there was a 2 degree difference between it and the other digital temp readers. Had to play around with where it sat in the tank for it to be happy and stop giving me the low flow warning. I have a really strong flow filter. The light showing function (temp warming to, temp at, error message) never went off creating light 24/7. Going back to my other heater.

Rated 5 out of 5 stars
By Finsup on Apr 8, 2025
Received Free Product

An Aquarium Hearter for Fresh or Salt Water

The Fluval E300 gas hands down been the best heater I've used in my 20+ years of having aquariums. To me the best feature is that it is totally submersible. This

The Fluval E300 gas hands down been the best heater I've used in my 20+ years of having aquariums. To me the best feature is that it is totally submersible. This heater has suction cups on the side to hold it in place, another big plus. The toggle is red which makes it easy to find and adjust. Its color changing screeen lets you know whether the temperature is in a safe zone or needs to be adjusted. Easiest heater I've ever used, basically fool proof.

Rated 5 out of 5 stars
By CAllison on Apr 14, 2025
Received Free Product

Fluval E300 100gal, 300w aquarium heater

Temperatures stay consistent within a degree or two I have a 150gl fresh tank and live in the south where it stays warm most of the year and winter months mostly

Temperatures stay consistent within a degree or two I have a 150gl fresh tank and live in the south where it stays warm most of the year and winter months mostly only go down to 50* with very short stint's below that so I adjust accordingly. In a colder climate you would also need 2 of these for a 150 tropical tank to keep the water more level and avoid a big temperature drop. I keep two in my tank one is a backup that stays off until we drop below 40* on really cold months. I have been using Fluval for years and highly recommend this product for peace of mind when it comes to caring for your fish friends