The fluval e-series is the best aquarium thermometer on the market. I have a 30 year old 44 gallon fresh tropical water pentagon shaped aquarium. In my 29 gallon high, the 200 watt works great.

Led back-lit lcd display is nice and makes checking the temp very handy. Microprocessor control makes setting the temp easy, as well. Lighted digital display in tank is a bit unsightly, but it is easy to read.

Took me a while to finally purchase this due to all the bad reviews. I'm sure many have had defective units but these heaters are wonderful when functioning properly. I've never had that issue, so i think it's more about aesthetics than anything else....  Read More

It never fluctuates. Turning it down to 75 is fine, but since it will reset to 77 automatically after being powered off (or a power outage), that's somewhat annoying.

No problems with lf (low flow) warnings on the display or wild heating or cooling. I have to buy and place a wavemaker close to the heater and problem solved.

I suspect this was simply a faulty unit as i have a fluval 306 filter. Temp reading is always off.

The suction cup attachment method is nice. I like how well it hides in the hidden compartment of the flex 9. The only drawback is the size.

The thermostat is accurate on this unit. The heating dial is easy to click and turn. Just start on lower the lower setting and work your way up over a few days to desired temp.

Perfect minimalistic design for all-in-one nano reef acrylic tank. It keeps the temperature very accurate and heats the water quickly when i cleaned and refilled the tank.

The temp settings on the top are off so use another thermometer to set to desired temp. It doesn't matter how high i set the temperature for this 100 watt fluval heater, the tank temp never gets above 76-77.

The m200 heater looks like a glo stick in my tank. The top of the heater leans out of the suction cup. There isn't any place for the top to come out if you have a fluval spec aquarium.

The package says submersible. To me that means *the whole thing* can go underwater. That makes no sense to me and is borderline false advertising.