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Extended holiday returns
FREE refund/replacement until Jan 31, 2027 Learn more
FREE refund/replacement until Jan 31, 2027 Learn more
This item's return window has been extended for the holiday season: FREE refund/replacement until Jan 31, 2027
To qualify for a full refund, items must be returned in their original, unused condition. If an item is returned in a used, damaged, or materially different state, you may be granted a partial refund.
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Availability:
14 left in stock
Arrives
Monday, Nov 9
At a glance
- Condition
- New
- Size
- M50
- Dimensions
- 1.8 x 4.8 x 14.8 in; 9.86 oz
- Weight
- 9.92 oz
- Color
- Silver
- Material
- Ceramic, borosilicate glass
- Wattage
- 50 watts
- In the box
- Fluval M50 Submersible Glass Aquarium Heater (50 watts)
- Warranty
- 3 years; The Fluval M series Submersible Aquarium Heater is guaranteed for defective parts and workmanship for a period of 3 year. We reserve the right to repair or replace, at our option. This guarantee excludes damage, breakage of the glass tube or injuries resulting from negligence or other misuse. This warranty does not include responsibility for animate or inanimate matter contained in the aquarium and is limited to the heater unit only. This appliance is factory sealed, tampering will void warranty.
Features 5
- Precision Temperature Control: The Fluval M 50-Watt Submersible Heater features a computer-calibrated thermostat for consistent, accurate heating. The easy-to-adjust temperature control dial ensures a stable aquatic environment for your fish and plants
- Reflective Mirror Technology: Designed to seamlessly blend into your aquarium, this heater uses built-in reflective technology that mirrors surrounding colors, making it virtually invisible while maintaining tank aesthetics
- Durable & Safe Materials: Constructed with shock-resistant Borosilicate glass and a high-density ceramic heat sink, this heater is built to withstand aquatic conditions while ensuring even heat distribution for a safe and efficient heating solution
- Slim & Easy to Install: The Fluval M Series heater features a slim profile tube, making it simple to install and position discreetly in your aquarium. Its compact design ensures minimal space usage, allowing for an unobstructed tank view
- Ideal for Small Aquariums: With a 50-watt power rating, this submersible heater is perfect for freshwater and saltwater aquariums up to 15 gallons. Keep your aquatic environment warm and stable for healthy, thriving fish and plants
Description
Ensure a stable and comfortable aquatic environment with the Fluval M 50-Watt Submersible Aquarium Heater—a premium heating solution designed for aquariums up to 15 gallons. This heater features computer-calibrated thermostat technology for precise temperature control, while the easy-to-adjust dial allows for effortless customization. Made with shock-resistant Borosilicate glass and a high-density ceramic heat sink, it ensures even heat distribution and durability. The built-in reflective mirror technology blends into your aquarium, mirroring the surrounding colors for an unobtrusive look. Designed for both freshwater and saltwater tanks, this compact and easy-to-install heater provides reliable, efficient heating to maintain an ideal environment for your aquatic life.
Specs 18
| Material | Ceramic, borosilicate glass |
|---|---|
| Brand | Fluval |
| Color | Silver |
| Wattage | 50 watts |
| Item Weight | 9.92 ounces |
| Product Dimensions | 1.8 x 4.8 x 14.8 inches; 9.86 ounces |
| Item model number | M50 |
| Manufacturer | Rolf C. Hagen (USA) Corp. |
| Brand Name | Fluval |
| UPC | 015561107815 |
| Global Trade Identification Number | 15 |
| Item Highlight | Compact, Reliable Heating with Mirror Technology |
| Number of Items | 1 |
| Unit Count | 1 Count |
| Item Type Name | Submersible Heater |
| Model Number | M50 |
| Part Number | A781 |
| Material Type | Ceramic, borosilicate glass |
No specs match.
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Monday, Nov 9
Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
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Top Amazon Reviews
Great product!!! Great product!!!
Size: M50
I love this heater. I have been using it in my betta's tank for about a year, and so far, it has worked very well! This heater is not made for being completely submerged under water. The black and grey part (the part above the little wavy marks) must be above water, along with the cord. I put this heater right next to my filter so that the filter motor can move the warmed water around the aquarium evenly. This heater is, of course, automatic. It has a thermostat somewhere in it that tells it to turn on when the water is too cool and turn off when the water gets warm enough. When the heater is warming your tank water, there will be a blue light on the side, and when it turns on and off, it will make a clicking sound and the light will turn on or off. This is a very good heater for my five-gallon tank. I have it set at about 81 degrees, and it keeps my tank at a steady 78 or 79 degrees Fahrenheit (which is the perfect temperature for betta fish). I am very impressed!
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Reviewed in the United States on November 7, 2025 Reviewed in the United States on November 7, 2025 by Oklahoma Mom
Reliable and Low-Key (in the Best Way)
Size: M150
This Fluval heater is a solid piece of equipment. I’ve had it running for almost 2 years now and it’s still performing like a champ — keeps the water at just the right temp without any fuss. The borosilicate glass design is a nice touch — it blends into the tank much better than those bulky, obvious heaters. You can still see it, but it’s not screaming for attention. The temperature dial is easy to use and overall it feels well-built and dependable. If you’re looking for a heater that just works and doesn’t make your tank look like a science experiment, this is a great pick. Its a good size, nice and slim and definitely worth every penny.
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Reviewed in the United States on July 25, 2025 by Michael
Good heater from a reputable company
Size: M200
I really like how oversized these are it seems efficient - getting these dialed in on the temp requires another thermometer imo that is calibrated And I think the safest bet is an ink bird or equivalent as a backup thermometer Incase of it breaking and ending up stuck on - I don’t do this (maybe yet?) but for an exspensive or huge tank I would consider it
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Reviewed in the United States on March 18, 2026 by Beanieoh
Easy and Reliable, but watch your thermometer.
Size: M50
I’m really happy with the Fluval M50 heater for my 9-gallon tank. It keeps the temperature pretty steady, with only minor fluctuations of a degree or two. The indicator light is a nice feature, so you know when it’s actively heating. One thing to watch out for is that it heats the water a bit more than what I’ve set it to. I have it set to 76°F, but the water temperature hovers around 81-82°F. Just be mindful of this when setting it up to avoid overheating your tank. Overall, it’s a solid heater and does a great job keeping my tank warm.
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Reviewed in the United States on September 15, 2024 by Charlie
Good reliable heater.
Size: M200
This M series 200 watt heater is a bit overkill for my 32.5 gallon tank. But it works great! I however wouldn't rely on the temperature setting gauge on the device. The best way to properly setup a heater is to set it to come on at just the right temp you want it at. Then monitor the temps over the next few hours and raise or lower the dial to match the actual temperature you want. The dials are seldom that accurate on their own. Try to attach the suction cups near the top. Don't have the holder setting on the coil area as it can melt the plastic. Also don't let the heat bulb touch anything near it. It can damage whatever it touches and can be damaged if something is leaning on it when it turns on. Place this heater away from invertebrates and snails. They can be burned or killed if the heater turns on when they are crawling around on it. These M series Fluval heaters are good heaters and I've used different wattages of them for years. But if you use them, pay attention to your tank's temps. If they stick on, they can cook your inhabitants. If they don't turn on, your tank temp could also get too cold. These heaters also are not intended to change the temp of the tank water more than 10-15 degrees total over time. They should not be used for outside use or when the room temp is way below the temp you want your tank water. They are designed to heat a few degrees only. Be sure the glass tube is not cracked or broken. Water must not contact the inside of the tube.
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Reviewed in the United States on June 1, 2024 by Don Gray
Great price and a great brand.
Size: M200
Great heater, keeps the water temperature consistent. It's a decent size and the color looks nice. You could easily hide one of these if you flipped it sideways in a tank. Adjusting the temperature is easy , definitely worth the price.
Reviewed in the United States on May 30, 2026 by Amazon Customer
What happened to quality and reliability?
Size: M100
I just removed over 30% of the dirty water which I could have done a lot more, but didn’t thank heavens. I cleaned the tank and accessories to give it a fresh start for my new heater. The temperature dropped rapidly as I replaced the water but I had installed my new Fluval 100w heater for the 30 gallon tank I have. Then I started to panic as I was counting on the heater to bring it back up to the correct temperature. Instead, nothing. I followed the troubleshooting directions to no avail. In the return process, it asks if I’ve removed the item from the package and if I have the original packaging which I do, but it concerns me that they will just send it out to some other unsuspecting aquarium hobbyist. I highly recommend if you order this item, which unfortunately I cannot recommend, to test it out first before you did what I did. Make sure it’s covered as indicated in their directions in a container of water beforehand. My fish is 6 years old. I thought Fluval was a trusted brand. I also had issues with their HOB filter for this same tank. It clogs easily. I returned from a 10 day trip to Europe only to smell smoke coming from the room where my tanks are. The filter had overflowed and water ran down the back of the tank, onto my area rug and hardwood floor. Worst though, was it dripped onto my surge suppressor and was smoking! Ironically, the surge suppressor came from Amazon too as some obscure Prime Day deal. Well, that also was replaced with the trusted Belkin name. During this incident, I had a pet sitter come while I was gone so it’s not like I left them with no supervision but really?? Who knows how much longer until a fire could have broken out. This was during the time Fluval acquired Aqueon. And of course it wasn’t returnable through Amazon so I had to suck it up and buy another filter. But I went with the Tidal brand which I have in my 72 gallon tank. To get functioning, reliable items has been like rolling the proverbial rock up a hill. It’s the cost, time, and aggravation that is exhausting. I thought Fluval was a trusted brand? For me, it’s been problem after problem with several of their products and it’s just exasperating. I need a reliable aquarium heater. Not one I that I have to worry about. So now I have schlep this broken heater back to Staples and find a reliable heater. Like this shouldn’t be so hard. Oh, and if you pre-test it as I suggested, there is supposed to be an indicator light. I can’t say where it’s located as no light ever came on. But make sure your light works. And obviously you can feel when the heater warms.
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Reviewed in the United States on September 18, 2024 by Gem5858
Yeah fish are going nice and cozy
Size: M200
Really like this product very heavy seems to work very well
Reviewed in the United States on May 8, 2026 by Judy Clark