Hi Aaron,
This was my dream filter during my recent filter search in January. I had decided that the 500 litres/hour flow rate was good and strong without disturbing the plants I hope to grow and the unit is not overburdend with features that might break, thus being more irritating than they would be worth.
I wanted an external with heating in order to begin the process of removing as much gear as possible from the aquascape view to make it more natural and knew that you have to think about that problem early in the process.
Everything was going along great until I found that the Ehiem Professional model line, unlike the Professional II product line, was very difficult to find and obtain in the USA. I had to resort to a special weekend where I dialed every local fish shop in the country that had phone numbers in the fish magazines. Finally that technique paid off and I found a knowledgeable shop on the other side of the country that I worked with.
During that process, my dealer went to someone that sounded like the regional distributor. In the discussion the ensued, the distributor was very firm that the Thermofilter version must not be used with any salt content in the water. He/She emphasized that the sensor in the Thermo versions was not guaranteed to sense the temperature correctly if there was any salt content.
I will probably not ever use salt in my aquarium, not currently having any interest in stocking brackish species, but the idea that I would be in trouble if I ever did venture into this need was disturbing and ultimately put me off using the Eheim thermo version. One could always leave it unplugged and not use that function in the eventuality that it malfunctioned or failed. The filtration would be unaffected, but the expense and effort would have been a waste, and I subsequently found occasional references to people who had had failures of the heating function, iir.
So I dropped back to Plan B for heating, remembering that RDD had had good luck with Hydor external heaters, which would accomplish the same function of removing the heating gear from the aquascape, even though with a somewhat messier implementation. I acquired a Hydor external and so far it has been an awesome piece of equipment, able to raise large quantities of water to temp faster than I've ever experienced before and maintaining absolutely rock solid temperature control so far. It spliced easily into the output hose and has only been a little trouble in terms of hanging it behind the tank to keep kinks out of the hoses.
So I dropped back to the Eheim Professional model 2222 (same model just without the heating element) and that has been also an awesome piece of kit. The guys here are probably tired of hearing me say that I can't even feel any vibration with my hand, much less any noise from it. Of course its only 5 months old or so, so not a lot of time to get any wear and tear on the impeller or housing. I love this filter! Just about every aspect of the design leaves me with nothing more I would want. If I work at it I suppose the flexibility of the how the spraybar enters the tank could be improved, and there is an extra kit I could exlore related to that - but it hasn't bothered me enough to do that. I'm using the mechanical and biomedia choices that came standard with it so that I will have a baseline understanding of them.
Aaron, in hindsight I believe that moving up to the 2026 model, which is in the Professional II line, would have made things easier in my case. It would probably have been easier to acquire locally and the difference in flow rate I now believe would have made little difference, perhaps even being better. The Pro II line adds a couple more things that might fail, making it potentially more irritating, but in this game you just have to jump in and decide to do good maintenance and just be prepared to replace parts eventually if they fail. In general the reputation for all these seems statistically quite good judging by anecdotal evidence here on TFF.
Will be interested to hear how your thinking and experience proceeds,
~~waterdrop~~ (enthusiastic beginner and returnee to the hobby)
