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Fluval M 200-Watt Submersible Aquarium Heater

Curated from 110 real Reddit conversations

Refreshed on: February 14, 2025

Fluval M 200-Watt Submersible Aquarium Heater

Brand: Fluval

Price: $36

Snoop Score:

4.8

Sentiment

3.8

Popularity

4.5

Technical

4.7

Buy on Amazon for $36 See All Aquarium Heaters Reviews

As an Amazon Associate, I earn from qualifying purchases.

Snoop's Take

The Fluval M 200-Watt Submersible Aquarium Heater is designed to provide high-performance heating for both fresh and saltwater tanks. Utilizing innovative mirror technology, this sleek and compact heater not only maintains temperature but also enhances the aesthetic of your aquarium. Consumer feedback highlights the Fluval M as a "super reliable heater" with effective heat distribution. Many users appreciate the clear temperature indicators, stating that it "keeps the whole tank an even temp." However, there are concerns regarding safety and potential thermostat failures, with some users reporting significant incidents like overheating and smoke production. The mixed reviews underscore both the effectiveness and risks associated with aquarium heaters in general. Overall, while the Fluval M 200-Watt Submersible Heater has its strengths in reliability and performance, potential buyers should be aware of safety concerns and consider the testimonials before making a purchase. It may be recommended for those who prioritize performance but with caution due to the safety warnings noted in user experiences.

Not for you? Check out our other rated Aquarium Heaters

It's been super reliable for 4 years now.
Positive Feedback

I accidently forgot to turn mine off once when it was vertical during a water change, the water level got too low and the heater started smoking!
Negative Feedback

4.8

Fluval M 200-Watt Submersible Aquarium Heater

Buy on Amazon for $36

Freshwater Aquariums

5 / 10

Saltwater Aquariums

5 / 10

Marine Life Habitats

5 / 10

Small to Medium Tanks

5 / 10

See how this compares to all Aquarium Heaters

What it does well!

Key strengths users can’t stop talking about.

Super reliable heater

“It's been super reliable for 4 years now.”➕

Effective heat distribution

“I’d put it upright next to the intake and output so it spreads the heat.”➕

“Yep this is the way to go.”➕

“Keeps the whole tank an even temp.”➕

“that way you can get the best heat dispersal.”➕

Reliable indicator of heater status

“I really like the Fluval E series - because they temperature is lit up, and shows red = too hot, blue = too cold, green = good.”➕

Fluval E series heater is effective

“expensive but fluval E series has been great for me.”➕

Heater provides effective heating

“it works just fine.”➕

“When you get it to where you want it, you'll never have to touch it again.”➕

Fluval heaters have a reliable digital display

“Even just having the display on it makes me feel safer instead of a knob on older style ones you have to dial in.”➕

“I now have 2 heaters. Neither of which can quite keep it at temp on the warmest day so that if one fails on it can't cook them and if it fails off they won't freeze.”➕

Users report good experiences with Fluval heaters

“If one gets stuck on it still won't be enough to overcook the tank before I can address it.”➕

Where it needs some work!

Areas to watch—feedback on possible improvements.

Safety concerns with heater placement

“I accidently forgot to turn mine off once when it was vertical during a water change, the water level got too low and the heater started smoking!”➕

Thermostat failure leading to overheating

“I had a fluval heater cook a fully stocked 125gal rainbow fish tank, only survivors with plecos and a couple other bottom dwellers.”➕

General distrust of aquarium heaters

“These days I have no respect for heaters, and I encourage you to have the same philosophy.”➕

“Heater recs please!!!! I can't find one that seems reliable lol.”➕

“Man shopping for heaters is the biggest pain in the hobby for me.”➕

“Ugh I HATE shopping for heaters, and so many of them are terrible, especially for small tanks!”➕

Thermostat may be faulty

“If it's not heating up to the thermostat, then it's faulty.”➕

Installation can be cumbersome

“I ended up buying a cheap one of amazon with a protective cover. Does the job.”➕

“if this one doesn’t work i will never buy a fluval heater again lmao, 50 bucks for this.”➕

Concerns about heater placement safety

“I’d be very weary of doing this and double check the instructions first.”➕

Concerns about temperature control leading to overheating

“My heater boiled all my fish to death last night.”➕

“A display for the temp in this posted scenario would still have ended up in dead fish.”➕

“The only way to really protect the tank while away is to have an automatic power off in the tank.”➕

Mechanical failures can still occur in digital heaters

“Glad you’ve had good experiences, but mechanical failures are still a common thing with heaters.”➕

Heater may be defective

“It's defective, unplug it immediately.”➕

“DO NOT TURN THAT ON.”➕

“return it. It's not water proof.”➕

Heater caused significant damage and fish deaths

“Fluval P25 aquarium heater almost set my apartment on fire just half an hour ago.”➕

“Smelled smoke and tank turned black. Betta didn't make it😭 but that's so dangerous.”➕

“So glad my house didn't catch on fire! Unsure of I want to put all the work into establishing a tank again.”➕

“Glad everyone is ok, but starting to be concerned if a recall might be needed or is this to be expected with tank heaters?”➕

Heater produced smoke and burnt plastic smell

“This thing turned into some sort of torch, and thank the fuckin' universe I was home, and awake.”➕

Compare On All Talked About Dimensions

Product Name	Price	Score	See Details	Buy Now
AQQA Aquarium Heater 500W for 66-135 Gallon Fish Tanks	$25	7.3	Details	Buy
Fluval E 300 Watt Electronic Heater	$34	7.2	Details	Buy
HITOP 50W Adjustable Aquarium Heater	$11	7.1	Details	Buy
HiTauing Aquarium Heater - Submersible Fish Tank Heater	$37	6.8	Details	Buy
hygger Aquarium Heater with Digital LED Controller	$43	6.5	Details	Buy
Aqueon Submersible Aquatic Flat Heater 15 Watts	$7	6.5	Details	Buy
Dreyoo 2 Set Aquarium Fish Tank Heater	$23	6.0	Details	Buy
HITOP-Fish Hitop 100W Adjustable Aquarium Heater	$14	5.8	Details	Buy
HiTauing Aquarium Heater - 100W Fish Tank Heater	$24	5.8	Details	Buy
DaToo Aquarium Heater Adjustable 50W	$6	5.7	Details	Buy
Tetra 26446 HT Submersible Aquarium Heater	$7	5.4	Details	Buy
Aqueon Pro 300 Submersible Aquarium Heater	$48	5.4	Details	Buy
MarineLand Precision Heater for Aquariums	$13	5.0	Details	Buy
HITOP Compact Submersible Aquarium Heater - 200W	$19	4.9	Details	Buy
Fluval M 200-Watt Submersible Aquarium Heater	$36	4.8	Details	Buy
PULACO 25W Small Aquarium Submersible Betta Heater	$9	4.3	Details	Buy
Aqueon Aquarium Fish Tank Preset Heater	$18	4.1	Details	Buy
hygger Small Submersible Aquarium Heater 100W	$22	3.6	Details	Buy
Orlushy Submersible Aquarium Heater, 150W	$19	3.4	Details	Buy
FREESEA Aquarium Heater for Fish Tank	$27	3.0	Details	Buy
FREESEA Aquarium Fish Tank Heater 50W	$16	2.6	Details	Buy

Core Power Plays

The specs and strengths that make it shine.

People tend to write more negative reviews than positive ones.

“People are more likely to take the time to write a bad review on a product compared to writing a good one.”➕

Advice on heater positioning for better performance

“It will most definitely help you warm your tank.”➕

Mention of copepods as beneficial for fish

“they arnt a saving grace but they are damn good cuc and amazing enrichment/available as snacks to your fish.”➕

Anecdotal reports of customer service being helpful

“Fluval is a pretty good company I would imagine so I would definitely give them a call.”➕

Buyer’s Cheat Sheet

What to check before you click ‘Add to Cart.’

Consideration of visual appearance in heater placement

“Better distribution of heat and you don’t have to worry about unplugging during tank maintenance.”➕

Discussion about alternative cheaper heaters

“I’d be wary of cheap heaters.”➕

Advice to take it slow and test water regularly

“Take it slow and have fun and be ready for it to get really ugly before it gets pretty!”➕

“This is the best advice (take it slow) and have fun..”➕

Discussion on temperature fluctuation tolerances

“It’s only 5F or 2C variation. That’s just how much the temperature varies with heaters.”➕

Questions about heater replacement

“Do I need to replace my Fluval heater?”➕

“I don't think they are meant to be buried in the substrate.”➕

“Looks like it may be burnt out or close to it.”➕

Cautionary Callouts

Know the pitfalls before they catch you off guard.

Concerns about heater reliability

“Reviews on Amazon of breaking, catching fire an cooking pets. Recent reviews on Amzon are a nightmare.”➕

“I recently went down this rabbit hole and did some research. Reviews will generally be weighted tow”➕

“Thanks, the choices were many. Bought a Cobalt Aquatics Neo-Therm Pro Aquarium Heater 50w. For $29”➕

“Mine just saved my whole 40g from a busted heater.”➕

Inquiry about reliable heaters

“I need something reliable.”➕

Discussion on reliability of alternative temperature controllers

“Water temperature is a function of room temperature, material conductivity, and the energy the heater dumps into the water.”➕

“Another vote for inkbird.”➕

Guppies may react negatively to water quality changes

“I woke up this morning and the guppies were stressed, all swimming at the top and bunching in the back corners.”➕

“A pH crash 100% destroys your cycle.”➕

“The way they cling to the surface is a good indicator that something is fucking with their O2 absorption.”➕

“they’re literally trying to leave the water so something is very wrong.”➕

Discussions about pH changes affecting fish behavior

“this could def be a huge part of it. Interestingly my tank water itself is better, which is odd because I didn’t add a buffer.”➕

Encouragement and emotional support for fish care

“I don’t have any advice but wanted to say they are beautiful and I hope they pull through!”➕

Discussion about test kits and their importance

“you need accurate test results from reputable brand.”➕

“Those test kits really really suck, you are going to be spending around $150 on a test kit eventually.”➕