Experience with Hydor inline and fluval 406
Hazarrd, Brian is right about the Hydor eTH if you are looking for an inline heater. I have a 65 gallon with discus and plants so the temp needs to be precise at 82 and when necessary, go up to 88 or 90 for very short periods ( if I get a disease breakout or something). Before i had plants, my inline 300w maintained 86 degrees at all times, no problem. There is also no issues at all with the variable power flow settings from the Fluval into the return line of the tank. I have had two over the last 5 years.
Good stuff: extremely reliable, nice to have the heater and settings outside of the tank and completely accessible.
Things to watch out for: no temperature reader on the unit, so you still need a thermonmeter. Also, if it stops working or something goes wrong, you have to shut your filter down too, because it's in line, of course. So ALWAYS have a back up submersible heater. Most serious aquarists believe in that anyway as you probably know. The first Hydor I had started losing accuracy around 3 years in. Not bad. With my second one I always had an issue with slight leaking around the connector. May have been my fault but i have had to keep an eye on it for the last year and a half. It stopped working last August. I turned the unit into the off position and stuck an emergency submersible into the tank ( not following my own rules out of sheer laziness) My mistake was that I did not unplug the Hydor, and it was not plugged into my GFI extention outlet. A few weeks ago, when I had an arcing condition caused by my lighting ballast going bad, the Hydor caught on fire.....very scary situation. ....just shows us all how we have to really watch our electrical connections for our tanks and not take them for granted. Could have been fatal.....AnywY, it have me a new zest for my tank...I was just a bit bored.
So now I am in the market for a new heating approach and after all my research, I think I am going to get another Hydor and use a Digital titanium at the other end of the tank so I can see the temp reading all the time and also
not work my Hydor so hard. For the temp I need, it's worth it. I would definitely recommend the inline approach as long as you are ready to do an I line replacement every few years.
I know i gave you more than you asked for but I Hope this helped. Good luck.