Fluval M 150-Watt Submersible Aquarium Heater – Reliable, Compact Heating with Mirror Technology for Fresh & Saltwater Tanks Up to 45 Gallons

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!

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

Works great

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.

Have used these heaters for years on my tanks and they work well. I like the simple design and it is easy to adjust the temp, just turn the dial on the top. It is not completely camouflaged but the mirrored surface does reflect its suroundings and I like the silver color. The temp will fluctuate a couple degreees but not a big deal and expected due to temp changes in our home. The suction cups are sturdy and stay in place on the tank sides. The title of this add it says submersible, but on the heater itself it says to not submerse below this line. However I have used these for years submersed with zero problems. Fluval is a brand I trust. The size is perfect, not too long. I recenty bought the 200 watt and the length is about 10 inches. Fits nicely on the side of the tank. Another brand I bought (starts with an E) was much longer and I had to put it in diagonally. Not sure why the size is so different but I like the shorter size. The thing I dont like about this heater is that the top is too big. If I place it vertically following the directions with the dial out of the water, the top of the heater hits the rim of the tank. I like to have the dial within easy access, but it will not fit following their directions in any of my tanks. It would fit If they designed it so that the suction cup holder held the heater at more of a distance from the tank side or if they made the top narrower. Another thing to consider is that this heater has no plastic guard on the bottom. The bottom may bump on the tank sides. Both of the suction cups are attached to the plastic holder which fits on the heater, you can't change the distance between the suction cups. So if the fish swim by quiclky they can bang the bottom of the heater on the tank side. My fish are pretty big and can hit it petty hard- they have shattered the bottom of every glass thermometer so I switched to digital. Tried sliding the holder further down but the holdef fits too loosely and the heater is top heavy, so I added another suction cup at the bottom of this heater just to be safe. For the price I think this a good heater.

I've only had this heater for a month and already need to buy a new one. It was working fine the first week or so and kept the water a consistent temperature but I began to notice the temperature creeping down this past week. When I took the heater out to check it, I saw the heater was actually melting the suction cup holder!! It smelt like burning plastic. This could've killed my turtle and/or eventually started a fire!!! Very upsetting considering all of the seemingly positive reviews. Can't even return and get my money back because the return window ended two days ago.

I have a 100-watt M in a 9-gallon shrimp tank set at 72.5 degrees and it keeps water temp at 76.5 which is needed. My new 150 watt is set at around 80.5 and it keeps water temp at 76.5 and my Angel fish is content with good appetite. I own all three fluval heaters and fluval M has the best (profile) dam best looking heater out there I think, and closest wattage for my 36-gallon tank. Once you tweak settings you can sit back and enjoy.

After trying several different aquarium heaters, this Fluval M 150‑watt model is the only one that has consistently kept my 10‑gallon tank at the correct temperature. It heats evenly, stays stable, and doesn’t fluctuate the way other brands did. For a small tank that needs dependable temperature control, this has been the most reliable option I’ve used. For ambient air context, it's winter and the house dips to 60 degrees at night. I have a cover on the tank which is essential.

This is an amazing heater, I’ve gone through probably 5 different brands of other heaters that won’t keep a consistent temperature or won’t even work in general. Saw a recommendation for this brand/model and I love it! Super easy to use and to adjust temperature. Highly recommend

Formschön und einfach in der Handhabung. Sehr gut.

Très bon chauffage, aucun regret sur son efficacité

Better to buy a local heater from your near buy aquarium store .No proper warranty support provided by the co and seller in India .The co says to reach out to the seller to claim the warranty and the seller says one has to go to the co to claim the warranty . Beware all the aquarium enthusiast .

As expected from a well known company for aquatics.