What's the best heater for a fluval flex 123l

[nathanm]

My room is usually between 18 and 21 degrees Celsius.

 

[Rocky998]

The fluval M series is good. Its been heating my tank up really well... The 100 watt should do it.

 

[Essjay]

I like Eheim heaters.

 

[raylove]

I'm currently using a Fluval and one I got from Maidenhead Aquatics - can't remember what it was called but it was effectively an own brand. It was quite cheap and I was a bit wary about buying it but it has performed superbly for several years now. I've had the Fluval for 18 months and that too has been great.
About 4 yrs ago I decided to treat myself and upgrade to what I thought was a top brand - Eheim. It was a disaster with wild temperature fluctuations with the thermostat sometimes switching on and off rapidly. After a few months it failed and I got a refund. In 50 years of fishkeeping it was the worst heater I had owned. I subsequently read the Amazon reviews - admittedly most are good, but about 10% report similar issues so I wouldn't trust another one.